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Qualitative Chemical 
Analysis 

A LABORATORY GUIDE 

BY 

WILFRED WELDAY SCOTT, A.M. 

EDITOR, “STANDARD METHODS OF CHEMICAL ANALYSIS” 

RESEARCH CHEMIST, GENERAL CHEMICAL COMPANY 
FORMERLY, CHIEF CHEMIST, BALDWIN LOCOMOTIVE WORKS, AND PROFESSOR 
OF CHEMISTRY, MORNINGSIDE COLLEGE 

i \ 

ILLUSTRATED 


THIRD EDITION 

COMPLETELY REVISED AND ENLARGED 



NEW YORK 

D. VAN NOSTRAND COMPANY 

25 PARK PLACE 





QU 73 



Copyright, 1910, 1913, 1918 
BY 

D. VAN NOSTRAND COMPANY 


OCT 21 ISIS 

©CLA506248 


/ 



THIS BOOK 


IS AFFECTIONATELY DEDICATED 
TO 

MY MOTHER 










































































PREFACE TO THIRD EDITION 

In this edition, the greater portion of the text has been re¬ 
written and new material added, although the general plan of 
the original work has been retained. Under “ Laboratory Exer¬ 
cises ” a large number of chemical equations have been introduced 
for the purpose of emphasizing the reactions. The lists of ques¬ 
tions at the close of each, group of elements have been enlarged. 
In Part V, tables of chemical compounds have been added. Part VI 
is entirely new. This includes the less common elements, which 
are important on account of their technical use. This section will 
be of value to those desiring an extended course in qualitative 
[analysis. 

The author trusts that this edition will prove useful as a class¬ 
room guide, and that it will offer concise and accurate information 
as a reference work in the field of qualitative chemical analysis. 

The author’s acknowledgments are due to Dr. J. C. Olsen 
for valued criticism and to Mr. J. P. Kelly for his* assistance in 
reading the proof. 

W. W. S. 

Grantwood, N. J., May, 1918. 


V 








PREFACE TO THE FIRST EDITION 


The purpose of this manual is to furnish a practical up-to-date 
uide for students studying qualitative analysis. The text em- 
iodies such methods of procedure in analysis as have been thor- 
•ughly tested and have proven themselves to be of practical value. 

The text is divided into five parts. Part I, the Introduction, 
iiscusses briefly the ionic hypothesis, theory of solution and those 
irinciples of physical chemistry which arc of frequent application 
n qualitative analysis. Methods and precautions to be observed 
n laboratory work are given. Part II is a systematic study of the 
3ASES. The following order is observed not only in the study of 
he metallic ions, but also of the acid radicals; a brief description 
)f the members of the group, special tests including only those that 
jerve to distinguish the substance, preliminary reactions leading 
jp to the detection of material in a combination, separation of 
he members of the group, a discussion of the methods used, and a 
inal list of questions covering certain important facts concerning 
the group. Part III takes up the study of the acid radicals. 
Part IV is a systematic method of analyzing an unknown sub¬ 
stance, beginning first with preliminary tests to gain valuable 
inferences that will shorten the methods, then analyzing the 
substance first for the bases it may contain, and finally its acids. 
Part V consists of tables of reactions for bases and acids. In 
Part II only such reactions were studied as lead directly to an 
isolation and detection of the substance, Part V is designed to 
meet the want of those desiring a more extended list of tests. 
The tabular form is easily followed and occupies but small space, 
affording an excellent reference chart for the analyst. The text 
is concluded with directions for preparing reagents used in the 
course and a table of solubilities. 


Vlll 


PREFACE 


The author believes that, since a course in qualitative anal; 
sis is preparatory to quantitative analysis, emphasis should 1 
placed on such methods as can be used in quantitative dete 
minations. The student should be taught the importance < 
careful, cleanly methods which are so necessary for reliable result 
The technic the student develops in this course will cling to hi] 
in after years. No subject brings out what is in an individu; 
more emphatically than does a course in qualitative analysi 
His patience is thoroughly tested, for he learns that the laws < 
nature are inexorable, and in order to get certain results coi 
ditions bringing them about must be closely adhered to or th 
tests will fail. The author has endeavored to make the directior 
of procedure explicit, so that they can readily be followed by 
beginner. No direction, however explicit, can supply the plac 
of an instructor, and it is sincerely hoped that students takin 
up the work will receive competent supervision. 

Wilfred W. Scott. 


Philadelphia, Pa., 
January, 1911. 







CONTENTS 


PART I 

PAGE 

Introduction. Terms Employed. Fundamental Principles; Theory 
of Solution, Electrolysis, Hydrolysis, Complex Ions, Color Reactions, 
Chemical Equilibrium, Reversible Reactions, Mass Action, Repression 
of Ionization—Common Ion Effect, Solubility Product, Electromotive 
or Potential Series. Laboratory Directions; Dry Reactions; Heat¬ 
ing the Substance, Blowpipe Tests, Oxidation and Reduction, Film 
Tests, Flame Tests, Borax Bead Tests; Wet Reactions; Filtration, 
Suction, Asbestos Filter, Evaporation, Cleaning of Apparatus, Record¬ 
ing Results, Suggestions. 1 

PART II 

The Metals. The Groups, Reactions of the Groups, Separation of 


the Groups, Tabular Outline of Separation, Notes on Separation. 26 

Hydrogen Chloride Group; Description of the Elements—Lead, 
Mercury and Silver; Laboratory Tests and Chemical Reactions of the 
Group; Procedure for Separation of the Group; Notes on the Procedure, 
Review. 33 


Hydrogen Sulphide Group; Description of the Elements Bismuth, 
Cadmium, Copper, Antimony, Arsenic, Tin, with Characteristic Tests 
and Laboratory Exercises on their Chemical Reactions; Separation of 
the Members of the Group, Soluble and Insoluble Subdivisions; Notes 

on the Separations, Review. 45 

Ammonium Sulphide Group; Description of the Elements Aluminum, 
Chromium, Cobalt, Iron, Manganese, Nickel, Zinc, with Character¬ 
istic Tests and Exercises on their Chemical Reactions; Separation 
of the Members of the Group—Ammonium Sulphide, Hydroxide, 


Basic Acetate Methods; Notes on Procedures; Review. 81 

Ammonium Carbonate Group; Description of the Elements 
Barium, Calcium and Strontium with their Characteristic Tests and 
Exercises on their Chemical Reactions; Separation of the Group, 

Notes on the Separation; Review. 125 

ix 








X 


CONTENTS 


PAGE 

Soluble Basic Group; Description of the Elements Magnesium, 
Potassium and Sodium, and of the Ammonium Radical; Exercises on 
the Reactions; Method of Detection in a Mixture of the Alaklies; 
Notes on the Separation; Review. 134 

PART III 

The Acids. Survey of the Groups. The Volatile Acid Group; De¬ 
scription of the Members H 2 C0 3 , (HCN)HCIO, HN0 2 , H 2 Si0 3 , 

H 2 S, H 2 S0 3 , H 2 S 2 0 3 ; Exercises on Their Chemical Tests; Separa¬ 
tion; Review. 154 

Silver Nitrate Group; Description of the Acids HC1, HBr, HI, 
HCN, H 4 Fe(CN) 6 , H 3 Fe(CN) 6 , HSCN; Exercises on Tests of the 
Acids, Analysis of-the Group, Separation of the Halogens, Review ... 170 
Barium Chloride Group; Description of the Acids H 2 B0 3 , HF, 
H3PO4, H 2 S0 4 , with Exercises on Their Characteristic Tests; Analysis 

of the Group, Review. 184 

Soluble Acid Group; Description of the Acids HC10 3 , HN0 3 , 
HMn0 4 , with Exercises on Tests of the Group; Analysis and Review. 200 
Organic Acids; Description of the Acids HC 2 H 3 0 2 , H 2 C 2 0 4 , 
H 2 C 7 H 4 0 3 , H 2 C 4 H 4 0 , with Exercises on Characteristic Tests; Review. 
Studies of Reaction Limits. 207 

PART IV 

Systematic Analysis of a Substance; Preliminary Examination of 
a Solid Substance ; Combustion Tube Tests, Reduction Tests on 

Charcoal, Flame Tests, Borax Bead Tests, Sulphuric Acid Tests.211 

Preliminary Examination of a Liquid; Analysis of the Metals; 
Preparation of the Solution, Substances Soluble in Water, Acid-sol¬ 
uble Substance, Refractory Substances Insoluble in Acids, Alloys; 

Table of Separations. 221 

Analysis of the Acids; Rules on Solubilities; Preparation of the 
Solution for Acid Analysis, Preliminary Tests of the Groups, Tab¬ 
ulated Table of Tests. 229 

Interpretation of Results. 234 

PART V 

Tables of Reactions of the Metals and the Acids. Table of Com¬ 
pounds, Table of Solubilities. 240 












CONTENTS 


xi 


PART VI 

PAGE 


The Less Common Elements. Rarer Elements of the Hydrogen 
Sulphide Group; Properties and Tests for Gold, Platinum, Osmium, 
Palladium, Rhodium, Ruthenium, Molybdenum, Selenium, Tellurium, 

Tungsten. 293 

Rarer Elements of the Ammonium Sulphide Group. Properties 
and Detection of Cerium and Other Rare Earths; Properties and 
Detection of Glucinum (Berillium), Titanium, Uranium, Vanadium, 

Zirconium. 310 

The Rare Metals of the Alkali Group. Properties and Tests for 

Lithium, Rubidium, Caesium. 322 

Mendeleef’s Periodic System of the Elements. International 
Atomic Weights. Reagents in Solution and Solid Reagents, Prepa¬ 
ration of Special Reagents.'. 324 

Index. 331 




































QUALITATIVE ANALYSIS 


PART 1 

INTRODUCTION 

In the study of General Inorganic Chemistry the student 
has become familiar with the occurrence, physical and chemical 
properties of the more important elements and their combinations 
as acids, bases and salts. He has made a study of methods by 
which the common elements are isolated, as well as the synthetic 
processes of obtaining certain combinations. In the laboratory 
experiments he has become accustomed to handling such apparatus 
as is involved in the study of these substances. He is now ready 
to apply this knowledge to the field of Analytical Chemistry, 
which is concerned with the determination of the kinds of matter, 
and the quantity present in a given substance. The systematic 
examination of a substance to identify its constituents and ascer¬ 
tain their amounts is known by the term “Analysis.” Qualitative 
Analysis deals with the identification of matter, Quantitative 
Analysis with the quantity of one or more of the constituents 
present in the material examined. The purpose of this book is to 
furnish information which will enable the analyst to distinguish 
substances one from another. 

TERMS EMPLOYED IN QUALITATITE ANALYSIS 

Reagent.—This is a substance employed in the process of 
separation of elements or in their isolation and detection. 

Precipitation.—When an aqueous solution of a reagent is 
added to a solution of a substance undergoing examination, it 



2 


QUALITATIVE ANALYSIS 


may cause a readjustment of combinations that will produce 
an insoluble compound, which will be thrown out of solution 
or “ precipitate ” as a solid. In describing precipitates the 
following terms are used: fiocculent, when the precipitate has 
a flaky appearance; curdy, when it appears like milk curds; 
heavy, when it settles rapidly; granular, when it appears in 
fine grains; and crystalline, when transparent crystals are evi¬ 
dent. 

Reaction.—This is a chemical process involving a change in 
a substance. This process may be represented by chemical 
symbols in the form of an “ equation.” For example when 
hydrochloric acid is added to a solution of silver nitrate, a reaction 
takes place and the precipitate of silver chloride results, this is 
expressed by the equation AgN 03 +HCl= j AgCl+HN 03 - 

Filtration.—If the turbid solution, formed by precipitation 
of a substance, is poured on to a filter paper, placed in a funnel, 
the operation is called “filtration.” The liquid passing through 
the filter is known as the “filtrate” and contains the soluble 
matter, the substance remaining on the filter paper is the “ pre¬ 
cipitate ” or “ residue” 

When water is added to the residue on the filter paper to remove 
soluble constituents, and the extract removed from the residue, 
the process is spoken of as “ washing ” the precipitate or residue. 

Decantation.—This facilitates washing of a precipitate. This 
can best be accomplished by allowing the granular compound 
to settle, pouring off the clear, supernatant liquid on to the wet 
filter, adding more of the washing reagent (generally pure water), 
stirring, allowing the precipitate to settle, pouring off the liquid, 
and when the salt has been sufficiently washed, pouring the last 
washing with the precipitate on the filter. The washing solution 
should be added to the salt in small portions, to lessen its tendency 
to dissolve. The residue should be washed down from the walls 
of the filter into the apex of the cone. 

Digestion.—When two products are mixed hot or cold, and 



INTRODUCTION 


3 


llowed to react some time with frequent stirring, the process is 
poken of as “ digestion .” 

Appearance of Solution.—A solution is said to be “ clear ” 
dien it does not contain suspended matter. The solution may 
>e colorless or colored. 

Neutralization.—When a base and acid in solution are mixed 
n such a proportion that the resulting solution does not affect an 
ndicator such as litmus, the solution is said to be neutral. 

Pseudo-solutions.—Certain amorphous substances called col- 
oids dissolve to form pseudo-solutions in water. Arsenous 
sulphide, the hydroxides of aluminum and iron, are examples, 
rhe addition of a salt solution or an acid to pseudo-solutions will 
precipitate the colloids. Since colloids become denser and less 
soluble at high temperatures, it is well to precipitate them from 
lot solutions. 

Oxidation and Reduction.—Oxidation is the reaction by which 
>xygen or some non-metallic element is added to a substance, or 
lydrogen or some metallic substance removed. Reduction is the 
)rocess in which oxygen or some non-metallic element is removed 
rom a compound, or hydrogen added. By oxidation the charge 
•f a cation may be increased and by reduction it may be dimin- 
shed. 

Examples: 

Oxidation . 2 FeS04+H2S04+0 = Fe 2 (S 04 ) 3 +H 20 . Valence 

r e ++ raised to Fe + ++ . 

Reduction. FeCl 3 +H = FeCl 2 +HCl. Valence Fe +++ lowered 
d Fe ++ . 

Amphoteric Electrolytes.—These are substances which act as 
cids in the presence of strong bases or as bases in the presence 
f strong acids. Aluminum hydroxide is an example of an ampho¬ 
ric electrolyte. It may ionized in two ways: 

Al(OH) 3 Al(OH) 3 

ft+AlO,—-_| |_Al+ ++(OH) s - 




4 


QUALITATIVE ANALYSIS 


Strong acids, owing to their free hydrogen cations, repress the 
H + ion of the aluminate so that ionization takes place according to 
the reaction on the right; on the other hand, an addition of a 
strong base, owing to the concentration of the OH - anions in the 
solution, prevents the ionization of the weak base; hence the 
reaction represented on the left takes place. (See pages 3 and 12.) 

FUNDAMENTAL PRINCIPLES 

For understanding principles of analytical chemistry it is 
advisable to learn certain fundamental laws governing chemical 
action and physical changes in solution. 

Theory of Solution.—Solutions are homogeneous mixtures 
which cannot be separated into their constituent parts by mechan¬ 
ical means. We may have solutions of gases in gases, solutions 
of liquids in gases, solutions of solids in gases, solutions of gases 
in liquids, solutions of liquids in liquids, and solutions of solids in 
liquids. The quantity of the substance that will dissolve in a given 
solvent depends not only upon the amount of the solvent, but upon 
the nature of the solute and the solvent and upon conditions of 
temperature and pressure. One liter of water, for example, will 
dissolve 1148 liters of NH 3 , 503 liters of HC1, 79.8 liters of SO 2 , 
1800 cc. of CO 2 , 41.2 cc. of 0, 21.2 cc. of H, and 20 cc. of N, the 
temperature being 0 ° and the pressure 760 mm. Raising the 
presssure increases the solubility of the gas, but raising the tem¬ 
perature lowers its solubility; in cases of solids, however, rise of 
temperature increases solubility, with a few exceptions. Upon 
the fact that no two substances have the same dissolving value— , 
and this value depends upon certain conditions—are based many 
of the processes of separation and detection of the elements in 
qualitative analysis. The student has learned that when acids, 
bases, and salts are brought into an aqueous solution, they undergo 
a peculiar kind of disintegration, which does not stop with the 
formation of molecules, but extends to the dissociation of mole¬ 
cules into their component parts, called ions, to a greater or less 



INTRODUCTION 


5 


extent according to the nature of the substance. The dissocia¬ 
tion increases with the rise of temperature and with dilution, 
md decreases with concentration. Since electrical conductivity 
md chemical activity depend upon the ions, substances ionizing 
•eadily are good conductors and chemically active. Nitric, 
lydrochloric, and sulphuric acids are more active chemically than 
icetic, hydrocyanic, and silicic acids, since they ionize much more 
•eadily. Likewise potassium hydroxide and sodium hydroxide, 
vhich are highly ionized in solution, are stronger bases than 
unmonium hydroxide or organic bases, which dissociate feebly . 1 
rhe activity of acids is due to the hydrogen cation H+, and that of 
>ases to hydroxyl anion OH - . Most of the reactions studied in 
qualitative analysis are ion reactions. It is necessary to recog- 
lize the ions rather than the compounds as a whole. In practi- 
:ally all the salts the basic and acid components show exactly 
he same reactions, no matter in what combinations these radicals 
nay be. For example, chlorine is precipitated as silver chloride 
vhen silver nitrate is added to any soluble chloride which, ionized, 
'ives a chloride anion. NaCl, KC 1 , CuCl2, BaCl2, FeCL readily 
•espond to the silver test for chlorine. Likewise copper is pre- 
:ipitated by hydrogen sulphide as eopper sulphide from the solu¬ 
tion of a soluble copper salt such as CuS(>4, Cu(NOs)2, CuCL, etc. 
rhe identity of the substance is maintained in all its manifold 
;ombinations as long as it can form free ions in solution. The 
;ase of complex ions will be dealt with later. 

The student has learned that the ions and molecules in a solu- 
ion act in a manner very similar to the molecules of a gas in a 
:losed vessel. The activity of these particles produces what is 
mown as osmotic pressure, and enables the substance to diffuse 
n the solvent. This osmotic pressure, as in case of a gas, is 
ncreased by heat and by the concentration of the particles. The 

1 Relative degrees of ionization, NaOH and KOH = 1. 

Ca(OH) 2 , Ba(OH) 2 and Sr(OH), = .03. 

NH 4 OH = .O4I8; H 2 0 = .0i 6 2. 


6 


QUALITATIVE ANALYSIS 


boiling and freezing points of a solution are governed by the numbei 
of the particles in the solution; and since molecules and ions act 
alike in this particular, substances that dissociate into ions, 
the electrolytes have a greater effect than substances that do 
not dissociate, the non-electrolytes. 

Electrolysis.—The theory regarding the phenomena that take 
place when an electric current enters an ionized solution is based 
on the belief that the ions are electrically charged bodies with a 
definite amount of electricity according to the nature of the ion. 
For example, if a univalent metallic cation carries, say, one unit 
charge of electricity, then a divalent cation will hold two units of 
electricity, in both cases the charges being positive; and again, if a 
monovalent acid radical or anion carries a unit charge of negative 
electricity, then the bivalent anion would hold two units. Scienti¬ 
fic investigation shows that each ion carries, for its formula weight 
in grams, 96,580 coulombs per equivalent. The solution of a 
salt is neutral when the negative and positive electric charges 
present are equal in magnitude and opposite in effect. When 
electrodes are immersed in the solution, the anions are attracted 
to the anode, where their charge is neutralized, leaving them in 
the form of ordinary radicals,- which either escape as molecules 
in the form of gas or unite with the solvent to form acids. Like¬ 
wise the cations attracted to the cathode neutralize their charge, 
becoming ordinary atoms, which combine with their own kind, 
forming molecules of metals, which carry no charge and which in 
turn may react with the solvent, forming bases. 

Example: 

(a) Na2SC>4 in solution ionizes, forming Na2+ SO4—. 

(b) Electrodes immersed in the solution 

Cathode ( —) *— 2Na + | SO4 —> Anode (+). 

(c) With charges neutralized. 

At cathode 2Na+ reacts with solvent 2HOH—> f H 2 -f- 2NaOH 




INTRODUCTION 


7 


At anode 2 (S 04 ")+ 2 H 0 H->! 0 2 +2H 2 S0 4 . Oxygen es¬ 
capes and the acid ionizes. 

(i d ) The acid and base now react, since their ions H + and OH” 
combine to form the undissociated compound, water. 

2NaOH<=*2Na+ 20H“ 

H 2 S0 4 *=*S0 4 — 2H+ 

IT l 

Na 2 S0 4 2H 2 0 

The ions are now ready to repeat the process, so that the reaction 
is a continuous one as long as the solvent remains, so that in 
reality the electrolysis of water takes place. Metals which do 
not decompose water collect around the cathode as a deposit. 
Advantage is taken of this in the important electrolytic processes, 
such as electroplating, refining of metals, etc., and in processes of 
analytical chemistry. 

Hydrolysis.— Water is itself very feebly dissociated into the 
ions H + and OH”. Pure water at room temperature is one ten 
millionth normal with reference to hydrogen and hydroxyl ions. 
Now if a salt of a strong base (i.e. one whose solution gives a 
high OH - concentration) and a weak acid (i.e. one whose solution 
gives a low H + concentration) is dissolved in water, the solution 
will react alkaline j and again if a salt of a strong acid and a weak 
base are dissolved in water, the solution will react acid. The 
action is due to hydrolysis, a double decomposition involving the 
dissociation of water. The H+ cations of the water in the first 
case react with the weak acid anion forming the undissociated 
acid, while the OH” anions of the water, no longer bound, give 
the solution a definite basic reaction. 

Thus when KCN, a salt of a strong base KOH, and a weak 
acid HCN is dissolved in water the reaction may be represented 

as follows: , T 

KCN (Solid) KCN (Solution)’ +±K + CN 

HOH«=±OH- h+ 

It IT 

KOH HCN 


8 


QUALITATIVE ANALYSIS 


In the second case the OH - anions of the water react with the 
weak base to form the undissociated base, and the H + cations, 

The reaction may be represented as follows: 

FeCl 3 (Solid) <=> FeCl 3 (Solution) <=> Fe+ ++ 3C1~ 

3H0H ?=±30H~ 3H+ 

1T it 

Fe(OH) 3 3HC1 

We observe the reaction by the formation of a brown precipi¬ 
tate, ferric hydroxide. 

Complex Ions.—There are cases where the elements do not 
respond to their tests, since they are combined with some other 
element or elements in the form of a complex ion. For example, 
chlorine in the compound potassium chlorate does not give a pre¬ 
cipitate with silver nitrate, as it remains combined with the 
chlorate anion in the form C10 3 ~ e.g. KCIO 3 ionizes into K + C10 3 “. 
A test for CIO 3 - will, of course, indicate the presence of chlorine, 
but in order to test directly for this element the chlorate must 
be decomposed to a chloride which gives a free chlorine ion. 
Likewise, iron combined as a ferrocyanide or a ferricyanide will 
not respond to its tests. The salt K 4 Fe(CN ) 6 ionizes thus, 
K 4 + Fe(CN ) 6 . The ferrocyanide test will indicate iron, but 
a direct test can only be obtained by liberating the iron from the 
complex anion by decomposing the ferrocyanide. These facts 
go further to confirm the statement that analysis deals with ions 
whose behavior makes possible their identification. 

Color Reactions.—The color of precipitates or of ions in solution 
frequently is characteristic. Color changes may be due either to 
a non-ionized condition of a substance or to ions. The indicator 
phenolphthalein, existing as an un-ionized acid in the presence of 
free hydrogen ions of another acid, is colorless, whereas its anion 
is a deep purple which becomes evident in the presence of the 
hydroxyl anions of a base. Undissociated litmus acid is red, its 
anion is blue. Un-ionized ferric hydroxide is brown, Fe +++ is 
pale yellow, Fe++ is green, Fe (CN) a -yellow, Fe(C 2 0 4 ) 2 -“ 




INTRODUCTION 


9 


red. Though CNS“ is colorless, the iron salt which dissociates 
but slightly is a deep red. The copper ion Cu ++ is blue, 
Cu(NH 3)4 "*""** deep blue, which is reduced by the addition of 
KCN to the cuprous ion Cu, which has no color. Co+ + ions 
are pink; Ni ++ are green. A number of the ions have no color, 
e.g. Ca++, Mg++, OH“, Cl", Br“, S0 4 “, N0 2 “, C10 3 - Oxida¬ 
tion or reduction may cause a color change; monovalent per¬ 
manganate ion is a deep blue, whereas the divalent cation Mn + + 
is faint pink; the green chromium salts oxidized form the yellow 
chromates; Cr ++ cation green changes to Cr0 4 anion yellow. 
The phenomenon of fluorescence is attributed to the ions of a 
solution. 

Chemical Equilibrium—Reversible Reactions.—Our attention 
thus far has been directed towards simple reactions. The ques¬ 
tion that now arises is, what reaction takes place in a mixture of 
two soluble salts such as potassium carbonate and sodium sulphate 
where no chemical change is evident? For a reply we turn again 
to the ionic theory; since both of these salts are highly ionized as 
well as the salts formed by an interchange of the radicals so that 
a less dissociated combination cannot take place, we conclude 
that the salts simply dissociate into their ions, in sufficiently 
dilute solutions, and the products K + , Na + , S0 4 , and CO3 

exist in the solution. It makes little difference whether K2CO3 
and Na 2 S0 4 or K 2 S0 4 and Na 2 C0 3 are used; the solutions in 
either case will be the same, the conditions being constant. 

A second case arises where it is possible for a product to form 
in a mixture, which dissociates to a less degree than the original 
substances in the solution. A reaction here may be evident either 
by a precipitate forming, or a gas being evolved, or a color reaction, 
or by the formation of an invisible, slightly dissociated soluble 
compound, the reaction being recognized by the change of tem¬ 
perature when the two solutions are mixed, or by the decrease 
in electrical conductivity. The reaction, however, may not go to 
completion. For example, when barium sulphate, a compound 






10 


QUALITATIVE ANALYSIS 


extremely insoluble in water, is mixed with a strong solution of 
sodium carbonate, the following double decomposition takes 
place: 

£a£0 4 +Na>+ C0 3 — £aC0 3 +Na 2 + S0 4 —. 

That is to say, the reaction is reversible, the substances under¬ 
going a forward and backward reaction until the opposing ten¬ 
dencies in the solution reach a condition of equilibrium where the 
quantity of each of the substances BaSCU, BaC(> 3 , 2Na + , CO 3 
and SO4 — remain constant, although the molecules and ions may 
continue to react. Under what conditions, then, will a reaction go 
to completion? In a broad sense a reaction goes to completion 1 
when one of the resulting substances is removed as rapidly as it is 
formed in the solution. This is the case when a gas is formed, or 
an undissociated molecule such as a very weak acid or base; or, by 
the union of H + and OH - ions of an acid and base, water 
being formed, or, by the formation of a difficultly soluble salt, 
a precipitate being thrown out of solution. 1 In all cases the ions 
react and not the molecules. 

The following examples illustrate each of the above con¬ 
ditions : 

Gas formed: 

Zn+ + +H 2 + S0 4 ——>Zn ++ S0 4 —+H 2 1. 
Undissociated molecule: 

Fe+ + + C1 3 -+3K+ CNS-—>3K+ Cl-+Fe(CNS) 3 j . 

Water formed: 

Na+ OH-+H+ N0 3 “ —> Na + N0 3 -+tf 2 0j. 

Precipitate formed: 

Ba+ + Cl 2 - +K 2 + S0 4 —->2(K+Cl-)+£a£0 4 i. 

Advantage is taken of such reactions in the detection and sepa¬ 
ration of substances in analytical chemistry. 

1 The terms are only relative. We have learned that even water dis¬ 
sociates slightly. No compound is absolutely insoluble. 


INTRODUCTION 


11 


Mass Action.—The Law of Mass Action may be stated as 
follows: The speed of the chemical action between two substances is 
proportional to the molar concentrations in the solution. 

This important law is worthy of consideration. The following 
concrete cases will make it more clear. When a simple com¬ 
pound such as sodium chloride is dissolved in water, it ionizes 
into the cations Na + and the anions Cl~. Concentration of these 
ions causes a reverse action to take place, resulting in the formation 
of the undissociated molecules NaCl. When the solution reaches 
the point of saturation, a further concentration causes precipita¬ 
tion of the salt. According to the Law of Mass Action, the speed 
at which this action takes place is dependent upon the concentra¬ 
tion of the reacting substances Na and Cl. The law may be 
[Na+] [Cl 


expressed by the formula 


NaCl 


= K, that is to say, the 


product of the ionic concentrations divided by the concentration 
of the undissociated molecules is constant. (Temperature remain¬ 
ing constant.) 

A good example of the reaction between two compounds to 
illustrate the law is the reversible reaction 


BaS 04 +Na 2 C 0 3 <—- BaCOa-j-Na.SCb. 

Let a, b, c, d represent concentration of the reacting substances 
in the order given in the equation. Let k and k' represent the 
constants depending upon the tendency of the substances to 
combine, and S and S' the speed of the reactions, and K the equi¬ 
librium constant. Then from the Law of Mass Action we have 
S = abk, and S' = cdk'. But since equilibrium has been reached, 
the speed of the reaction in both directions is the same, so that 
S and S' may be eliminated; then abk = cdk', or 


— = —. Since 7 ~ = K } therefore ^- = K. 
ab k' k ab 


From the above it can be seen that by increasing either c or d 







12 


QUALITATIVE ANALYSIS 


more, ab would have to form to restore equilibrium, and the 
reaction would reverse. The reaction would go forward by 
increasing a or b. Advantage is taken of this law when an excess 
of sodium carbonate is added to barium sulphate when the con¬ 
version of the latter to a carbonate is desired. The same thing 
could be accomplished by removing one of the resulting con¬ 
stituents. 

Repression of Ionization—The Common Ion Effect.—From 

the Mass Law we can readily see that ionization may be repressed 
by adding to a solution a salt having a common ion with that of 
the solute. This may be shown in an interesting way by adding 
concentrated hydrochloric acid or a strong solution of sodium 
hydroxide to a saturated solution of sodium chloride. In either 
case a copious precipitate of NaCl takes place. In the first case 
we have increased the concentration of the anions Cl - , in the 
second case that of the cations Na + . Reverse reactions take 
place to restore equilibrium, forming undissociated molecules 
NaCl. But since the solution is already saturated with the salt, 
precipitation immediately takes place. 

Another interesting example is the repression of the ionization 
of the weak base ammonium hydroxide by addition of ammonium 
chloride, a salt with the common ion NH 4 + . Advantage is 
taken of this fact in preventing precipitation of Mg (OH) 2 by 
NH4OH in both qualitative and quantitative analysis—ammonium 
hydroxide added to a water-soluble magnesium salt will pre¬ 
cipitate Mg(OH)2; if however, sufficient NH4CI is present, mag¬ 
nesium hydroxide is not precipitated, since the addition of NH4CI 
increases the NH 4 ions in the solution, and, by the common ion 
effect, represses the hydroxyl ions of the base NH 4 OH, so that 
there are insufficient hydroyl ions for the solubility product of 
Mg(OH)2 to be exceeded; magnesium therefore remains in 
solution. 

Solubility Product.—Salts do not have to be extremely soluble 
in order to ionize; even a difficultly soluble salt such as silver 


INTRODUCTION 


13 


chloride dissociates to a slight extent in pure water, e.g. AgCl 
dissolves slightly and forms ions Ag + and Cl“. 


_ [Free ions Ag + ] [Cl ] 

AgCl Ag Cl > e.g. jj n( jj gs0 ci a t,ed molecules AgCl 


The product of the concentration of the ions Ag + XCl is 
known as the solubility product. These two values jointly 
determine the extent of the solubility of the substance. 

The following principles apply to precipitation and solution of 


substances in terms of their solubility product. 

Exceeding the solubility product, by addition of a compound 
with a common ion will decrease the solubility of the precipitate. 


\ 


For example, the addition of HC 1 to the water containing the 
precipitate AgCl will render it less soluble. Hence, in precipitat¬ 
ing silver chloride an excess of hydrochloric acid is used when it is 
desired to remove silver from a solution; for the same reason an 
excess of silver nitrate is added to a solution when it is desired to 
remove the chlorine ions. 

Precipitation of an electrolyte takes place when its solubility 
product is exceeded. For example, when ammonium oxalate is added 
in excess to a solution of calcium chloride, a precipitate of calcium 
oxalate takes place. The solubility product of the calcium oxalate 
is easily exceeded, the anions of the ammonium oxalate in excess 
furnishing the conditions necessary. Calcium oxalate in solution 
ionizes into Ca ++ C2O4 . This may be expressed the equation. 


[Ca+ + ] [C 2 Q<—1 
CaC 2 0 4 


=K. 


It is evident that increased concentration of the ions C2O4 
necessitates for formation of more of the unionized CaC 2 0 4 in 
the presence of (NH 4 ) 2 + C 2 0 4 “ in excess. The solution soon 
becomes saturated, and calcium oxalate precipitates. 

Solution of a precipitate takes place on the addition of a substance 
that decreases the product of ionic concentrations below the solubility 








14 


QUALITATIVE ANALYSIS 


product of that compound. For example, if hydrochloric acid is 
added to the precipitate of calcium oxalate, the salt dissolves. 
This is accounted for by the fact that HC 1 is highly ionized, 
whereas H2C2O4 dissociates but feebly, and scarcely at all in the 
presence of free H • anions, e.g. in the presence of an acid such as 
HC 1 . Hence the anions of calcium oxalate combine with the 
hydrogen cations of HC 1 , forming the weak acid H2C2O4. The 
removal of the C2O4 anions from solution reduces the product 
of the concentrations of Ca+ and C2H4 —, ions in solution below 
the solubility product of CaC 20 4 causing the precipitate of cal¬ 
cium oxalate to dissolve to establish equilibrium. The reaction 
continues until all of the precipitate goes into solution. 


Unionized CaC 2 0 4 —>ions Ca ++ C 2 0 4 —. 

Ca++ C 2 0 4 --+2(H+ Cl") ->Ca++Cl 2 -+tf 2 C 2 0 4 . 

Silver chloride dissolves in ammonia water on account of the 
formation of the complex cation Ag(NH 3 ) 2 + causing the removal 
of the Ag cation from Ag + Cl - , thus decreasing the solubility 
product. 

In general, an insoluble salt of a given acid will interact and 
dissolve when treated with a solution containing another acid that 
is more highly ionized, provided the salt is not one of extreme 
insolubility. CaC 2 0 4 dissolves in HC1, but not in HC2H3O2, 
since oxalic acid is weaker than hydrochloric acid but stronger than 
acetic acid. On the other hand, BaS 04 is insoluble in HC 1 , since 
it is an extremely insoluble salt. 

Electromotive or Potential Series—The paragraph on elec¬ 
trolysis dealt with the separation of the elements of an electrolyte 
by means of electromotive force. The tendency of 
Potassium metals, however, is to pass from the free element to 

Lithium the ionic condition ‘ This tendency varies according 

Blrium t0 the element ‘ 

Strontium The following list on the left gives the metals 
Calcium arranged in the order of the most active to the least 



INTRODUCTION 


15 


Magnesium 

Aluminum 

Manganese 

Zinc 

Cadmium 

Chromium 

Iron 

Cobalt 

Tin 

Nickel 

Lead 

Hydrogen 

Antimony 

Bismuth 

Arsenic 

Copper 

Mercury 

Silver 

Palladium 

Platinum 

Gold 

powerful 
ence of a 


active of the series. The ones preceding have a 
greater tendency to ionize than the ones succeeding, 
and will displace the latter in their combinations, 
when added to solutions of their salts, liberating the 
positive elements in metallic form. 

Zinc, for example, placed in a solution of silver 
nitrate, will cause silver to crystallize out, e.g. 

Zn-|- 2 AgN 03 —► Ag2+Zn(N03)2. 

Only the metals above hydrogen will displace it from 
the ionic state; that is to say, these only are attacked 
by acids with liberation of hydrogen. For example 
iron reacts with hydrochloric acid, bismuth does not. 
The elements below II, however, are attacked by cer¬ 
tain oxidizing agents. HN0 3 , for example, forms 
oxides with the metals Cu, Sb, Bi, Hg, and Ag, which 
oxides in turn are readily acted on by the acid, form¬ 
ing soluble ionized salts and undissociated water. 
The noble metals Pd, Pt, and Au are attacked by 
oxidizing agents such as chlorine liberated in the pres- 
catalytic agent. 



16 


QUALITATIVE ANALYSIS 


LABORATORY DIRECTIONS 


The student of qualitative analysis should be familiar with the 
laboratory processes involved in the study of general inorganic 
chemistry. Believing this to be the case, the author has inten¬ 
tionally omitted detailed directions of such processes; however, 
he deems it advisable to mention, in a cursory manner, some of the 
important operations involved in the laboratory. 

Qualitative analysis involves two kinds of tests, (a) dry reac- 
tions, and (b) wet reactions. 

Dry Reactions. These tests are applied to the solid, dry sub¬ 
stance before its ions are tested in solution. A compound may 
frequently be detected by this method. 

Heating the Substance.—The dry material is placed in a hard 
glass test tube and heated directly in the Bunsen flame. Sub¬ 


limation may take place or the mate¬ 
rial may decompose, changing in 
color, or giving off gas which can be 
recognized by certain characteristics. 
Ammonium chloride heated in a 
test tube will illustrate sublimation. 
Heating mercuric oxide shows a color 
change of the solid, together with 
decomposition with the evolution of 
oxygen. 



Blowpipe Tests.—The following 
illustration (Fig. 2) shows the struc¬ 
ture of the flame, a knowledge of 


Fig. 1.—Bunsen Burner. J hlch 1S . essential in blow-pipe or 

flame oxidation and redimt.inn 


ui uiiuurnea caroon. see Fig. 3. 












INTRODUCTION 


17 


Oxidizing Flame is obtained by inserting the blowpipe nozzle 
ito the center of the flame and blowing as before. The flame 



--Higher oxidizing flame. Excess of oxygen bvit 
not as hot as the lower oxidizing flame 


• ~Zone of complete combustion 


—Lcrmmocrs point of reducing flame 
—Reducing flame 
• -Hottest portion of the flame 
—Lower oxidizing flame. Excess of oxygen 
—Gnburned gas 
—Low temperature 


Fig. 2.—Structure of the Flame. 




should now be colorless, due to complete combustion of the carbon. 
The tip of the flame will now be an oxidizing flame. See Fig. 4. 









18 


QUALITATIVE ANALYSIS 


The material to be tested is placed in a small hollow on a piece 
of charcoal. Reduction to the metallic state occurs when the 
reducing flame is blown steadily on the compound. 

Metals may be oxidized by the non-luminous tip of the oxidiz¬ 
ing flame. 

A special tip that flattens the flame is used for blowpipe 
tests. 

Flame Oxidation and Reduction without the Blowpipe.—Oxi¬ 
dation and reduction flame tests can be made directly in the Bunsen 
flame without the use of the blowpipe, a process generally more 
successful in the hands of the beginner. 

The pulverized material is thoroughly mixed with sodium 
carbonate (fused), and a minute portion picked up on the end 
of a splinter of wood specially prepared for the test. The material 
is inserted into the reducing flame for a few moments, then lowered 
into the cool zone of unburned gas until it cools slightly, then 
removed, scraped off, and examined. A blowpipe test should 
be made, using a crystal of copper sulphate of silver nitrate. 

Thick wooden matches may be prepared for the reduction 
test as follows: Boil the matches for half an hour in a strong 
solution of two parts of sodium carbonate to one part of alum. 
Remove and dry. Now coat each match (head removed) two- 
thirds of its length with sodium carbonate by rubbing it into the 
melted salt. Now hold the coated match in the flame, revolving 
the splint rapidly. Repeat the operation until the match is 
thoroughly coated. Char it slightly, and place aside for use. 

Film Tests.—These tests may be best made by condensing the 
volatile product on the cold surface of a porcelain evaporating dish 
filled with cold water. Reduction tests are made by dipping a 
thread of asbestos into the substance to be reduced, and inserting 
it into the reducing flame, and at the same time holding the dish 
immediately over the tip of the reducing flame (Fig. 2). A 
reduced metal will leave a metallic stain on the porcelain. This 
deposit should be examined and tested. For example, arsenous 



INTRODUCTION 


19 


xide is reduced to black metallic arsenic. The spot is readily 
oluble in a drop of bleaching-powder solution. 

Oxidation tests are made by simply raising the porcelain dish 
util the tip of the oxidizing flame impinges against it. A fresh 
ample of the material is held in the reducing flame on a thread of 
sbestos. The reduced metal is reoxidized as it passes up through 
he oxidizing flame, and deposits as an oxide film on the porcelain 
iish. As the test takes but a few seconds, the dish remains cold, 
o that the volatile products readily condense upon it. 

Flame Color Tests—One end of a fine platinum wire two or 
hree inches long is fused into a glass rod of convenient length. 
Che test is made by dipping the wire into the material to be tested 
xd inserting it into the flame. Since chlorides are volatilized 
eadily, the material is best moistened with strong HC1 before 
naking the test. The color of the flame frequently leads to the 
letection of a metal, especially a member of the alkaline earths 
)r the alkalies. The examination of the flame by means of the 
spectroscope is of especial importance, since each metal has its 
>wn characteristic spectra. 

The platinum wire should be thoroughly cleaned by repeatedly 
lipping it into concentrated hydrochloric acid and holding it in 
•he Bunsen flame, or better still, in the flame of a blast lamp until 

10 color is imparted to the flame. 

Borax Bead Tests.—A platinum wire, similar to the one men¬ 
tioned under Flame Color Tests, is used in the Borax Bead Tests. 
The free end of the platinum wire is coiled in a small loop, through 
which an ordinary match will barely pass. The loop is inserted 
into the flame until white hot, then plunged into powdered borax. 
It is now held in the hottest part of the flame. The borax swells 
and melts into a crystalline bead. The material examined is picked 
up on the bead and tested, first in the reducing flame, then in the 
'oxidizing flame. The color imparted to the bead may lead to 
important conclusions as to the substance. The student is advised 
to make tests with salts of nickel, cobalt, iron, and copper. 





20 


QUALITATIVE ANALYSIS 


Wet Reactions.—These tests are made with substances ir 
solution. The greater portion of our course in qualitative analy¬ 
sis deals with wet reactions. The following hints will be o: 
value. 

Filtration.—A fine precipitate will clog the filter paper anc 
render the process of filtration slow and tedious; therefore it it 


i BQTQ51 



Test Tube. 



b 

Erlenmeyer Flask. 


Fig. 5. 



c 


Wash Bottle. 


necessary to have the particles as large as possible. This is accom¬ 
plished by adding the precipitating reagent to the hot solution of 
the salt and allowing the mixture to cool slowly, whereupon the 
small particles dissolve and larger crystals form. Before filtering, 
it is well to heat the solution almost to boiling, as hot water filters 
more rapidly than cold water. The paper should be moistened 
before it is used, as the first portion of the filtrate is apt to be 
turbid if poured on a dry filter. The fiilter is made as follows: 











INTRODUCTION 


21 


rhe circular filter paper is folded in half and again folded 
vith one edge overlapping, as shown in Fig. 8. The corner of 
he short fold is torn off so that the 
japer fits the funnel snugly at the base 
>f the cone, avoiding a crease, which 
vould permit air being drawn in. Air 
ucked in on the edge of the paper 
•etards filtration. 

Suction.—The filter pump is used to 
idvantage in filtration. To prevent the 
liter paper from tearing, a platinum 
jone is placed in the funnel before in¬ 
serting the filter. A small Buchner 
‘unnel may be used in place of the ex- 
Densive platinum cone. 



Beaker 


Fig. 6 .—Method of Filtering. 





Platinum 

Cone. 


Buchner Funnel. 



Filtering by Suction. 


Gooch Crucible. 


Fig. 7. 


Where a filter pump is not available, filtration is hastened by 
lengthening the funnel tube, thus increasing the hydrostatic 



























22 


QUALITATIVE ANALYSIS 


pressure due to the column of water that forms in the tube durir 
filtration. 

Asbestos Filter.—When strong acids are used in dissolving 
precipitate, and it is necessary to filter the solution without dill 
tion, an asbestos filter should be used. This filter is made b 
pouring clean, long-fibered asbestos, suspended 
in distilled water, over a Witt plate or a wad 
of glass wool placed in a funnel connected to 
a filter flask and suction pump and drawing 
down hard. The filter should not be more 




Folding of Filter. 


Filtering Funnel. 


Fig. 8. 


than one-tenth of an inch in thickness. A Gooch crucible or 
Buchner funnel may be used. 

(Impurities of the asbestos are removed by HNO 3 , HC1 an< 
distilled water used in turn.) 

Evaporation.—A porcelain dish or casserole should be use, 



Porcelain Dish. 



Fig. 9. 
















INTRODUCTION 


23 


/hen it is necessary to evaporate a solution to small bulk, and 
specially when the solution is evaporated to dryness. Glass 
3 apt to crack when the liquid is driven off from the solid material. 

Operations which cause the evolution of disagreeable gases 
hould be conducted in the hood. 

Cleaning of Apparatus.—The importance of using clean appara- 
us cannot be over-emphasized. The glassware should never be 
)ut away dirty. A few minutes should 
>e given at the close of the laboratory 
>eriod to “cleaning up.” The glass 
hould be cleaned with chromic acid 
leaning mixture, followed by tap water 
nd then distilled water. Before putting 
t away it should be wiped dry with a 
lean towel, or tissue paper. Test tubes 
nay be conveniently placed in a rack 



Fig. 10— Test-tube Rack. 


Fig. 11.—Test-tube Brush. 


ade for this purpose. See Fig. 10. The tubes are cleaned out 

7 means of a brush. „ 

Recording Results.— The student should keep a record of all 
lalvsis of “unknown,” e.g., the solids or solutions given to him for 
lalysis by the members of the laboratory staff. Neatness in 



















QUALITATIVE ANALYSIS 


24 

keeping such records should be insisted upon. The following form 
has been found convenient: 


Substance and Precedure 

Result 

Indication 

Conclusion 

Orig. sol.+HCl 

Ppt. 1 +hot water 

Ppt. 2 + NH 4 OH 

Sol.2+K 2 Cr0 4 

Sol. 3 +HNO 3 

White ppt. 1 
Ppt. 2+sol. 2 
Black ppt. 3 
+ sol. 3 
Yellow ppt. 
White ppt. 

HC1 group 

AgCl, HgCl+PbCU 
Hg+HgNH 2 Cl and 
Ag(NH s ) 2 + Cl- 
PbCrO, 

AgCl 

HC1 group presenl 

Hg present 

Pb present 

Ag present 


Example of Report of an Unknown 
Group Members Found to be Present 


HC1 

Ag, Hg, Pb 

H 2 S (a) 

Pb 

(6) 

None 

(NH 4 ) 2 S (a) 

None 

( b) 

None 

(NH 4 ) 2 C0 3 

Ba 

Soluble 

Na, K 

Acid ions 

N0 3 , C0 3 


Name of the analyst. 

Place and date. 

Suggestions. The descriptive sections afford a ready reference 
for those desiring a brief outline of properties and occurrence of 
the elements. A list of the more common compounds will be 
found in Part V. A comparison of the solubilities of these com¬ 
pounds will be found helpful in the study of reactions. 

The student should be required to write out the reactions 
involved in the preliminary tests of the elements. These reactions 
should enable him to understand the processes involved. 

As classroom work is essential to the course, the pupil should 
be prepared to recite upon the topics suggested at the close of 
each group, and be able to give the reasons for the steps involved 
in the separation of the elements. 












INTRODUCTION 


25 


CLASSROOM REVIEW 

1. Define the following, giving examples illustrating the terms: 
Residue, filtrate, precipitate, chemical reaction, ion, oxidation, 
reduction, neutralization, decantation, clear solution.. 

2. What is meant by hydrolysis? 

3. What is a complex ion? 

4. When is a reaction said to be reversible? Give an example 
of a reversible reaction. 

5. What is meant by mass action? 

6. State laws governing the solubility of a compound in a 
given solution, giving examples illustrating the laws. 

7. Give an example showing the use that can be made of the 
knowledge of the potential series of elements. 

8. Outline the structure of a Bunsen flame, showing the 
zones of the flame, the hottest and coolest portions, the oxidizing 
and reducing zones. 

9. Why is it important to keep the glassware clean? 

10. Why is it an advantage to have the precipitate coarsely 
granular rather than fine, or gelatinous, a washing of the precipi¬ 
tate being desired? 

11 How are bead tests made? Film tests? Flame tests? 

12. What is an amphoteric electrolyte? 





PART II 


THE METALS 

The metals are the bases that form the positive ions of salts in 
solution. These elements are recognized by characteristic com¬ 
binations with certain acid radicals forming difficultly soluble salts, 
and, in a few cases, by colors produced by the fomation of com¬ 
plex cations. 

The metals are classed under five divisions on account of their! 
deportment towards certain general reagents. These groups are 
first isolated and, by subsequent processes of elimination, the 
individual ions are recognized. It is thought best to designate 
these groups by the names of the precipitating reagents, and in 
case of subdivisions by terms expressing a common property of 
the members. 

A number of the metals occur so rarely that they are omitted 
in elementary courses of qualitative analysis. These are included 
below in brackets. The groups are characterized as follows: 

Hydrogen Chloride Group 

Metals whose ions unite with Cl“ to form insoluble chlorides: 
Silver, Ag+; Mercury, Hg+; Lead, Pb + +; (Tungsten, W; Thal¬ 
lium, Tl; Tantalum, Ta; Molybdenum, Mo; Tellurium, Te). 

Hydrogen Sulphide Group 

Metals whose ions unite with S to form sulphides that 
are insoluble in dilute mineral acids. 

(a) Insoluble H 2 S Subgroup: Sulphides insoluble in (NH 4 ) 2 Sx 
Mercury, Hg++; Lead, Pb++; Bismuth, Bi+++; Copper, Cu ++ ; 

26 











THE METALS 


27 


admium, C< 


Cd ++ ; (Rhodium, Rh; Palladium, Pd; Osmium, Os; 


luthenium, Ru). 

( 6 ) Soluble H 2 S Subgroup: Sulphides soluble in (NH 4 ) 2 Sx. 
,rsenic, As +++ , As +++++ ; Antimony, Sb + + + ; Sb +++++ , Tin, 
n ++ , Sn +++ + ; Gold, Au + , Au +++ ; Platinum, Pt ++ , Pt ++++ ; 
Iridium, Ir; Molybdenum, Mo; Tellurium, Te; Selenium, Se). 


Ammonium Sulphide Group 1 

Metals whose ions unite with S~ to form sulphides that 
,re insoluble in NH 4 OH in the presence of NH 4 C1. 

(a) Precipitated as hydrates by NH 4 OH: Iron, Fe + + + ; Alumi- 
mm, Al +++ ; Chromium, Cr+ ++ ; (Glucinum, Gl; Cerium, Ce; 
S T C odymium, Nd; Praseodymium, Pr; Erbium, Er; Lanthanum, 
L,a; Columbium, Cb; Scandium, Sc; Tantalum, Ta; Titanium, Ti; 
Thorium, Th; Yttrium, Yt; Ytterbium, Yb; Zirconium, Zr). 

(b) Precipitated as sulphides by (NIELS: Nickel, Ni ++ ; 
Cobalt, Co + + ; Zinc, Zn + + ; Manganese, Mn ++ ; Iron, Fe ++ ; 
(Uranium, U; Indium, In; Thallium, Tl; Gallium, Ga; Vana¬ 
dium, V). 


Ammonium Carbonate Group 

Metals whose ions unite with CO 3 to form carbonates 
insoluble in NH 4 OH in the presence of NH 4 C1; Calcium, Ca ++ ; 
Strontium, Sr++; Barium, Ba++. 

Soluble Basic Group 

Metals whose cations do not readily combine with anions to 
form insoluble salts and are not precipitated by a common reagent: 
Magnesium, Mg ++ ; Ammonium, NH 4 + ; Sodium; Na+; Potas¬ 
sium, K + ; (Lithium, Li; Caesium, Cs; Rubidium, Rb.) 

1 The valences are given for the forms in which the elements are iso- 
lated. For the other valences, see pages 81-108. 




28 


QUALITATIVE ANALYSIS 


LABORATORY EXPERIMENTS 


When a chemist analyzes a substance, he first examines the 
solid by spreading it out upon white glazed paper and notes 
whether it is homogeneous or heterogeneous. If the substance 
is a mixture, he endeavors to find out the number of different 
substances present, and is frequently able to detect substances 
by the color and crystalline form. Following the physical exami¬ 
nation he gives a small portion of the material preliminary tests, 
which often prove valuable in subsequent work and may prove 
conclusively the presence of certain elements. He is now ready to 
examine the substance systematically. He first dissolves the 
material and then, by a process of precipitation and solution, 
separates the ions into the general groups, and later isolates and 
identifies the individual members. He now makes tests for the 
acid radicals, his knowledge of the presence of certain metals 
being of assistance in this analysis. 


CHARACTERISTIC REACTIONS OF REPRESENTATIVE MEMBERS 
OF THE GROUPS 


As we have seen, the elements are grouped together in 
several general groups. Our study in this section will deal 
with a characteristic member of each general division to show 
why this grouping has been adopted in analytical chemistry. 

Hydrogen Chloride Group.—Silver will serve as a characteristic 
member of this group. 


• 1 * Pour 2 or 3 cc * of silver nitrate solution in a beaker and 
add about 10 cc. of water; now add dilute HC1 as long as a pre¬ 
cipitate will form. Stir the solution and allow to settle. Add a 
few more drops of HC1 to see that the reagent has been added 
m excess. Filter by decantation, pouring the last of the solution 
with the precipitate on the filter. Wash once by pouring a few cc. 
of distilled water on the residue. The precipitate is silver chloride. 


Reaction.—AgN0 3 +HCl = j AgCl+HN0 3 . 




THE METALS 


29 


2. Test the filtrate with the following group reagents in the 
ollowing order. Pass in H 2 S. Does a precipitate form? 

3. Make alkaline with NH 4 OH and add (NH^S. Does 
1 precipitate form? 

4. Now boil to remove sulphur, and filter if sulphur separates 
Dut. To the alkaline solution add (NH^COs* Evidently all 
:)f the silver is removed by the first reagent. 

Hydrogen Sulphide Group.—Copper is a characteristic mem¬ 
ber of the general group. Separation of the subdivisions of this 
s^roup will be taken up under the study of the general group later. 

5. Take 2-3 cc. of Cu(N0 3 ) 2 solution, dilute with water, and 
add HC1. Does a precipitate form? 

6 . Now pass in H 2 S as long as a precipitate forms. It is well 
to heat the solution, though not essential in this case. Filter 
and test the filtrate to see that all of the copper is removed by 
passing in more H 2 S. 

Reaction.—Cu(N 03 ) 2 ~} _ H 2 S = J. C 11 S 4 - 2 HNO 3 . 

7. If the work is carried on properly, the reagents, which 

are used to precipitate the following groups, will have no effect 
upon the filtrate from CuS, obtained in experiment 6 . Try these— 
(a) Add NH 4 OH and (NH 4 ) 2 S. ( 6 ) Add (NH 4 ) 2 C0 3 . 

Ammonium Sulphide Group.—Iron is a characteristic member 
of the general group. 

8 . Take 2-3 cc. of Fe(N 0 3 )3 solution, dilute with water, and 
add HC1, then pass in H 2 S. 

9 . Boil to expel H 2 S and filter if sulphur separates out, 
add HN0 3 to oxidize the iron, and heat to boiling. 

10. Make alkaline with NH 4 OH. The reddish brown pre¬ 
cipitate that forms is Fe(OH) 3 . 

Reaction.— F e (N O3) 3 4* 3 NH 4OH— »F e (OH) 3+ 3 NH 4NO3. 

11. Add (NH 4 ) 2 S. The precipitate turns black, due to the 
formation of FeS. 

Reaction.— 2Fe(OH)3+3(NH 4 ) 2 S= i 2FeS-f-S+6NH 4 OH. 


30 


QUALITATIVE ANALYSIS 


If sufficient reagent has been added, all of the iron will be 
completely precipitated. 

Ammonium Carbonate Group.—Calcium is a characteristic 

member of this group. 

12. Take 2-3 cc. of Ca(NC> 3)2 solution and dilute with a few 
cc. of water. Note the following facts: The reagents HC 1 , H2S, 
NH4OH, and (NH^S produce no effect upon the ionized salt. 

13. Add (NH 4 ) 2 C 03 . A precipitate is immediately thrown 
down. The white substance is CaC(> 3 . 

Reaction.—Ca(N0 3 ) 2 +(NH 4 ) 2 C0 3 = i CaC0 3 +2NH 4 N0 3 . 

If the solution is made acid by addition of HC1, the precipitate 
dissolves. 

The Soluble Basic Group.—Sodium is a characteristic member 
of this group. Use 2-3 cc. of NaN (>3 solution. Convince your¬ 
self that the metal is not precipitated by any of the reagents thus 
far used. 


SEPARATION OF THE GROUPS 

14. Make a mixture of the solutions of the metals studied 
above, e.g. 2 cc. of each of the following: AgN0 3 , Cu(N0 3 ) 2 , 
Fe(NOs)3, Ca(NC>3)2, and NaNC> 3 . Add dilute HC1 until no 
further precipitate forms and filter. Silver is removed as a 
chloride. 

15. Heat the filtrate nearly to boiling, and add H 2 S. Copper 
separates as black CuS. Test the filtrate to insure the complete 
removal of this group, refiltering if a precipitate forms. 

16. Expel H2S by boiling and add NH4OH; observe that the 
iron separates out. This will be in the form of green ferrous 
hydroxide. 

17. Oxidize by the addition of HNO3, boil, and again make 
alkaline with NH 4 OH. The precipitate will now be red Fe(OH) 3 . 

18. Add (NH4)2S. Black FeS is formed, and iron is com¬ 
pletely removed. 





V 


THE METALS 


31 


19. Boil the filtrate, and filter if a precipitate or residue 
separates out. Add NH 4 OH if the solution is not alkaline, and 
then add (NH 4 )2C0 3 . White CaC0 3 separates out and the 
filtrate contains the sodium. 

20. Evaporate to dryness to expel the ammonium salts, but 
do not heat to redness. This should be carried on in the hood 
in a porcelain dish. Test the sodium by the flame test. The 
flame is colored bright yellow by the metal. If possible, examine 
with a spectroscope. Note the brilliant yellow line. 


Outline Scheme for Separation of the Groups 

To the cold solution add dilute HC1 in excess. Filter. . 


Precipitate. —AgCl, HgCl, PbCl 2 . 


Filtrate. —Heat to boiling, and pass 
in H 2 S as long as a precipitate con¬ 


tinues to form. (Test filtrate by passing in more H 2 S.) Filter. 


Precipitate. — (a) HgS, PbS, Bi 2 S 3 , CdS, CuS. 
( b ) As 2 S 3 , As 2 S 5 , Sb 2 S 3 , Sb 2 S 5 , SnS, SnS 2 , etc. 


Filtrate.—Boil to expel 
H 2 S, and filter if sulphur 
separates. Add HNO : , 
and boil, then make alkaline with NH 4 OH. Iron, aluminum, and chromium 
will precipitate as hydroxides. Now add (NH 4 ) 2 S and filter. 


Precipitate. —FeS, Al(OH) 3 Cr(OH) 3 , CoS, 
NiS, MnS, ZnS. 


Filtrate. —Boil to small bulk 
and filter to remove sulphur. 
To the filtrate add NH 4 OH 


and (NH 4 ) 2 C0 3 , and filter. 


Precipitate. —CaC0 3 , BaC0 3 , SrC0 3 


Solution. —Mg ++ , Na + , K+, 
NH 4 + , Cs + acid radicals, etc. 





















32 


QUALITATIVE ANALYSIS 


NOTES AND PRECAUTIONS ON THE SEPARATION OF 
THE GROUPS 



Preparation for the Work.—Read thoughtfully the procedure and notes 
before attenpting an analysis. Time spent in the study of the methods 
will be amply repaid by quicker and more accurate results in the laboratory. 

Reagents.—Be sure that the reagents are properly labeled and free from 
impurities. For example, commercial hydrochloric acid would never do for 
qualitative work. 

Stoppers should never be placed on the desk, as they will not only soil 
the desk, but take up contaminating material which will thus find its way 
into the reagent. To prevent stoppers of KOH and NaOH reagent bottles 
from sticking, clean the stoppers, wipe dry, and coat with paraffin. 

Beakers and flasks should be labeled in order to keep track of the work. 
Confusion will be thus saved when running several tests. A careful record 
of the work must be kept as you proceed. 

Precipitates.—Until your results are passed upon, save the precipitates 
to verify your work. 

Decantation will hasten washing of a precipitate, as the solid is apt to 
clog the filter. Filtering solutions hot, whenever it is possible, is advisable, 
since it hastens the work. 

Filter paper should fit the funnel snugly, and not extend above its rim. 
It should be moistened with water before being used for filtering the solution. 

Funnels should have an angle of 60°, with a narrow stem about five inches 
in length. The hydrostatic pressure of the column of water in the stem 
hastens filtration. 

Washing the precipitate with small portions of water and allowing the 
precipitate to drain before adding more wash water should be observed. 

Filtrates should be tested with the group reagent to insure the complete 
precipitation of the group. 

To prevent splashing, have the stem of the funnel touch the side of the 
beaker or receiving vessel. This precaution is absolutely necessary in quanti¬ 
tative analysis, and should be followed now, as it will prevent careless work 
later. 

Evaporating the solution for tests of the sodium and potassium salts in the 
soluble group should be carried on in the hood, as the volatile ammonium 
compounds are disagreeable. 

Quantity of the reagents and of the solutions tested should be no 
more than is necessary. The skill of a chemist is determined by his suc¬ 
cess in detecting minute quantities of substances. Much time is saved in 
filtering, and a smaller quantity of the reagent is required for precipitation. 




HYDROGEN CHLORIDE GROUP 

Silver Group , Group 1, Hydrochloric Acid Group 

DESCRIPTIVE 

Common Metals.—Lead, Mercury (-ous), Silver. 

Rarer Metals—Molybdenum, Tantalum, Tellurium, Thallium, Tungsten. 

General Characteristics . 

The metals of this group belong to separate families in the 
periodic arrangement. The common elements—silver, mercury, 
and lead—are grouped together quantitatively on account of their 
comparatively insoluble chlorides, whereas the chlorides of the 
other metals are soluble in water or dilute acids. The sulphides 
of this group are also insoluble in dilute acids. 

Individual Characteristics. 

LEAD 

Pb, at.wt. 207.2; sp.gr. 11.34; m.p. 327° C.; b.p. 1625° C.; oxides, PbO, Pb0 2 , 

Pb 3 0 4 . 

The soft, bluish-gray metal is easily cut with a knife. When freshly 
cut the metal is bright, but soon tarnishes in moist air, due to surface oxida¬ 
tion. Lead may be easily melted in the Bunsen flame (m.p. 327° C.) 

Hot, dilute nitric acid is the best solvent of the metal. Lead nitrate 
is insoluble in concentrated nitric acid, but dissolves readily upon dilution 
with water. The metal is insoluble in dilute sulphuric acid, but dissolves 
in the hot, concentrated acid. Although not soluble in dilute hydrochloric, 
it dissolves in the hot, concentrated acid, especially in presence of the halo¬ 
gens chlorine, bromine, and iodine. The metal is soluble in glacial acetic 
acid. 

The following salts are but slightly soluble in water, PbC0 3 , PbCl 2 , 
2PbC0 3 • Pb(OH) 2 , PbCr0 4 , Pb 3 (P0 4 ) 2 , PbS0 4 , PbS, PbW0 4 . The compounds 
dissolve in hot dilute nitric acid. A list of the more common lead com¬ 
pounds and their solubility, color, and form is given in Part V. 

33 


34 


QUALITATIVE ANALYSIS 


DETECTION 

Hydrochloric acid precipitates lead incompletely from its cold solution 
as white PbCl 2 , soluble in hot water, by which means it is separated from 
mercurous chloride and silver chloride. PbCl 2 forms needle-like crystals 
upon cooling the extract. 

Hydrogen sulphide precipitates black PbS from slightly acid solutions 
along with the other elements of the group. 1 Yellow ammonium sulphide, 
sodium sulphide, and the fixed alkalies dissolve out arsenic, antimony and 
tin. The sulphide of lead, together with bismuth, copper, and cadmium, 
dissolve in hot dilute nitric acid, leaving mercuric sulphide insoluble. After 
addition of sulphuric acid, the extract evaporated to dryness and then to 
S0 3 fumes, expels nitric acid. Upon adding water to the residue and 
boiling with a little additional sulphuric acid, the sulphates of bismuth, 
copper and cadmium are dissolved out, lead sulphate remaining as a white 
residue. 

Confirmatory Test.—Lead may be further confirmed by dissolving the 
sulphate in ammonium acetate (barium sulphate is very slightly soluble), 
and precipitating the yellow chromate, PbCr0 4 , by addition of potassium 
dichromate solution. 

MERCURY 

Hg, at.wt. 200.6; sp.gr. 13.696; m.p. -38.9° C.; b.p. 367.33° C.; oxides, 

Hg 2 0, HgO 

Mercury is a liquid at ordinary temperatures. It becomes a solid at 
-38.9° C. The metal remains bright at ordinary temperatures, but may 
be oxidized by application of heat in presence of oxygen, changing to a yel¬ 
lowish red color. 

Nitric acid is the best solvent for the metal and its amalgams. The oxides 
are insoluble in alkalies. Mercuric oxide is dissolved by acids. Hydro¬ 
chloric acid forms mercurous chloride with the lower oxide, insoluble in 
dilute hydrochloric acid. 

Mercury has a valence of one and two, forming two series of salts. The 
mercurous halogen salts are but slightly soluble in water, whereas the mer¬ 
curic halogens are soluble excepting the iodide, which is difficultly soluble. 

1 Lead precipitates best from solutions containing 1 cc. of concentrated 
free hydrochloric acid (sp.gr. 1.19) for each 100 cc. of solution. The sul¬ 
phide is appreciably soluble if the acidity is increased to 3 cc. HC1 per 100 
of solution. 


THE METALS 


35 


The sulphides Hg 2 S and HgS are practically insoluble. See list of com¬ 
pounds in Part V. 

DETECTION 

Metallic Mercury is recognized by its physical properties. It is the 
only metal which is a liquid at ordinary temperatures. The element forms 
a convex surface when placed on glass. 

Hydrochloric Acid Test, Hg + .—Mercury in the mercurous form is pre¬ 
cipitated by hydrochloric acid as white mercurous chloride, HgCl. This 
compound is changed by ammonium hydroxide to the black precipitate of 
metallic mercury and nitrogen dihydrogen mercuric chloride. 

Hydrogen Sulphide Test, Hg + + .—Mercury in the mercuric form is not 
precipitated by hydrochloric acid. The sulphide of the element is thrown 
out from an acid solution as black HgS. The precipitate first appears white, 
changing to orange-yellow, then brown and finally to black, as the H 2 S gas 
is passed into the solution. The element is distinguished from the other 
members of the group by the insolubility of its sulphide in yellow ammonium 
sulphide and in dilute nitric acid. 

Mercurous Chloride.—If the mercury sulphide obtained above is dissolved 
in aqua regia, the nitric acid expelled by adding hydrochloric acid and 
evaporating to dryness, the residue taken up with a little hydrochloric acid, 
diluted with water, and treated with a solution of stannous chloride, a 
white precipitate of mercurous chloride is first formed, which is further 
reduced to metallic mercury by an excess of the reagent. 

Metallic copper, iron, zinc, displace mercury from its acid combination 
in solution, the metal Hg depositing over the surface of the displacing metal. 
See Electromotive Series in Introduction, page 14. 

SILVER 

Ag, at.wt. 107.88; sp.gr. 10.57; m.p. 960.5° C.; b.p. about 1960° C., 

oxides, Ag 2 0, Ag 2 0 2 

Silver is a white, ductile, malleable metal, harder than lead, but easily 
cut with a knife. It is a good conductor of electricity and heat. The metal 
does not tarnish in the air under conditions affecting metallic lead, but in 
; presence of H 2 S and moisture the metal turns dark, due to a coating of Ag 2 S. 

Solubility.—Nitric acid, dilute or concentrated, attacks silver rapidly 
when hot. The presence of a soluble chloride, iodide or bromide in the sol¬ 
vent or substance will retard and may prevent solution. Unless oxidizing 
agents are present, dilute sulphuric acid has practically no action on massive 
silver, but hot, strong acid commences to be an active solvent at a con- 


36 


QUALITATIVE ANALYSIS 


centration of 75 per cent H 2 S0 4 . Hydrochloric acid attacks silver supe 
ficially. The action of alkaline hydrates or carbonates in solution is ina I 
preciable; in a state of fusion, slight. 

The halogen salts of silver are practically insoluble in water. A chan/ 
of color occurs when the salts are exposed to light. The cyanide, ferro ar 
ferricyanide and the sulphide are also difficultly soluble in water. Attentic 
is called to the list of more common silver compounds given in Part V. 

DETECTION 

A trace of silver in most substances may be detected by furnace ass£ 
methods. 

A silver salt fused on charcoal with Na 2 CC >3 is reduced to metallic silver j 

The wet method of detection of silver most commonly practiced, depern 
upon observation of the properties of the precipitate formed by the additic 
of slight excess of alkaline chloride to a cold nitric or sulphuric acid solutic 
of the substance undergoing examination. One-tenth milligram of silvr 
precipitated as silver chloride in a cold 200-cc. acid solution gives a vei 
perceptible opalescence to the liquid. 

Silver chloride is white when freshly precipitated, tinted pink whe 
palladium is present; in colorless liquids on exposure to light turns brow] ' 
violet, blue or black. By agitation, heating or long standing the precipital I 
becomes coagulated or granular and in such a state is retained by an ord i 
nary filter. The presence of some forms of organic matter prevents coaj 
ulation. 

Silver chloride is dissolved by concentrated hydrochloric acid; raisin j 
the temperature of the acid assists the action. It is dissolved by sodiui 
thiosulphate, alkali cyanides, mercuric nitrate, and alkaline chlorides. 

From mercurous chloride, silver chloride, except when constituting 
small proportion of the precipitate, is distinguished by its solubility withou 
decomposition in ammonia. Precipitation from its ammoniacal solutio { 
isaccomplished by acidifying. 

It is distinguished from lead chloride by its flocculated appearance 
PbCl 2 is granular or appears as needle-like crystals. AgCl is practicall 
insoluble in hot water in presence of a little HC1, PbCl 2 dissolves. 

Silver Thiocyanate. Silver, in a cold solution containing free nitric acic 
only a small amount of colored salts, and no mercury, may be detected throug 
the formation of a white precipitate, similar in appearance to silver chlorid j 
by addition of a slight excess of an alkaline thiocyanate. 












THE METALS 


37 


LABORATORY EXERCISES 

Chemical Reactions 
LEAD 

1. To a few cc. of a solution of a lead salt [Pb(N 03)2 or 
5 b(C 2 H 3 C 2 ) 2 ] add HC1—The white precipitate is PbCl 2 . 

Reaction.—Pb(N0 3 ) 2 +2HCl = | PbCl 2 +2HN0 3 . 

2. Wash once by decantation with cold water, then add more 
yater and boil; the precipitate slowly dissolves. Look up the 
olubility of PbCL in list of compounds in Part V. 

3. Decant the clear liquid through a filter and divide in two 
>ortions. Allow one to cool; PbCb crystallizes out in fine needles. 

4. To another cooled portion add a few drops of H2SO4. The 
trhite precipitate is PbSCU. 

Reaction.—PbCl 2 +H 2 S0 4 = 1 PbS0 4 +2HCl. 

5. If PbS0 4 is dissolved in NH4C2H3O2 and a solution of 
I 2 CrC >4 or K2Cr 2 0 7 is added, a yellow precipitate, PbCr 04 will 
»e thrown out of the solution. 

6. PbS 04 is soluble in HNO3, KOH, NH4C2H3O2. PbCrCU is 
oluble in KOH, but not in HC2H3O2. Test solubility of lead 
ulphate with the reagents stated. 

Pb(C 2 H 3 0 2 ) 2 +K 2 Cr0 4 = | PbCr0 4 +2KC 2 H 3 0 2 . 

MERCURY 

7. Use soluble mercurous salt, LIgN0 3 . Add HC1—the white 
>recipitate is HgCl (calomel). 

Reaction.—HgN0 3 +HCl = { HgCl+HN0 3 

8. Wash the precipitate by decantation to remove HC1, then 
>oil with water and filter off the clear solution. 


38 


QUALITATIVE ANALYSIS 


9. Test the filtrate for mercury by passing in H 2 S; the present 
of mercury is indicated by a black precipitate of HgS+Hg. 
negative test indicates the insolubility of HgCl in hot water. 

Reaction if Mercury is Present.— 2 HgCl+H 2 S = Hg2S+2HCl 

Hg 2 S= i HgS+Hg 

10. Add NH4OH to the HgCl precipitate in a beaker. T1 
precipitate turns black, owing to the formation of mercur 
ammonium chloride and free mercury. 

Reaction. — 2 HgCl+2NH 3 = 1 NH 2 HgCl + Hg+NH 4 C1 

11. Pour off the ammonia, wash once by decantation and ad 
aqua regia; the precipitate dissolves, forming the soluble HgC 
(corrosive sublimate). 

Reaction.— NH 2 HgCl+Hg+5Cl = T N+2HgCl 2 +2HCl 

12. Boil the solution to expel the excess of aqua regia. Dilu 
with a few cc. of water and add SnCl 2 solution. The precipita 
is HgCl, white. SnCl 2 in excess gives Hg, gray. 

Reaction.— 2 HgCl 2 +SnCl 2 = 2 HgCl +SnCl 4 
2 HgCl+SnCl 2 = 2 Hg + SnCl 4 

SILVER 

13. Use a solution of AgNC> 3 . Add HC1—the white curdy pr 
cipitate is AgCl. 

Reaction.— AgN0 3 +HCl = j AgCl-f-HN0 3 

14. Add water and filter by decantation to remove free HC 
add more water and boil and again filter. 

15. Test the filtrate for silver by passing in H 2 S. Does a pr 
cipitate form? If silver is present a black precipitate will forr 
Or add KI, in presence of silver a yellow precipitate, Agl w 
form. The tests will be negative in absence of silver, which w 
be the case if AgCl has been completely precipitated. 





THE METALS 


39 


16. Add NH 4 OH to the precipitate placed in a test tube; 
he precipitate dissolves owing to the formation of the soluble 
lilver ammonium chloride, Ag(NH 3 )2Cl. Upon acidifying this 
dear solution with HN0 3 , silver chloride is precipitated. 

Reactions. — AgCl+2NH 3 = T Ag(NH 3 ) 2 Cl 

Ag(NH 3 ) 2 Cl+2HN0 3 = | AgCl+2NH 4 N0 3 

TABLES OF REACTIONS 

Tests of the elements are given in Part V. The arrangement in the form 
>f tables enables the student to make a comparison of the reactions of members 
)f a group with reagents used in their isolation and detection. 

Example. —The first table gives the comparison reactions of the Hydro¬ 
gen Chloride Group. 

Ten tests are given for lead, the solution of lead nitrate being indicated 
it the top of the second column, and the list of reagents in the first column, 
rhe reagents used are HC1, NH4OH, H 2 S, K 2 Cr0 4 , K 4 Fe(CN)c, Na 2 C0 3 , 

STaOH, SnCl 2 , H 2 S0 4 , Zn. , 

The resulting reactions are shown in the second column m fine with the 

reagent used. 

The same reagents are applied to the solutions of mercury and silver. 
The tables may be used for laboratory tests if so desired. 


40 


QUALITATIVE ANALYSIS 


Outline of the Procedure for the Separation of Mercury (Ous) 
Lead and Silver 

From the laboratory tests it is evident that the chloride 
of the metals, mercury in its lower valence, lead and silver ar 
precipitated when a soluble chloride is added to a solution cor 
taining these elements. By filtering off the precipitates a separa 
tion from other substances that may be in solution is effectec 
The fact that lead chloride dissolves in hot water while th 
chlorides of silver and mercury (ous) do not, makes it possible t 
separate lead from silver and mercury by boiling the mixei 
chlorides in water and filtering. Lead may be recognized i: 
the filtrate by adding dilute sulphuric acid, which forms th 
water-insoluble, white PbS0 4 , or by adding a soluble chromate 
which precipitates yellow PbCr0 4 . If lead is present in suf 
ficient quantity, cooling the extract causes the formation c 
needle-like crystals of PbCl 2 . A separation of silver chlorid 
from mercurous chloride is accomplished by treating the mix 
ture with ammonia; the silver chloride dissolves with formatio: 
of the water-soluble compound Ag(NHs) 2 Cl and is removed b; 
filtration. Silver is recognized by neutralizing the NH 4 OH ani 
the NH 3 of the silver compound, with HNO 3 . Mercurou 
chloride is converted to a black substance. NH 2 HgCl+H 
by the ammonia. Confirmation of mercury is accomplishe* 
by dissolving the substance in aqua regia and treating th 
HgCl 2 , thus formed, with SnCl 2 , whereupon a white precipitat 
of HgCl, or gray precipitate containing metallic^ mercury, prove 
the presence of this element. 





THE METALS 


41 


Procedure of Separation of the Hydrogen Chloride Group 


To about 15 cc. of the cold neutral or acid solution of the original dissolved 

! substance add 5 cc. HC1 (1.12). Shake and allow to settle. Filter, washing 
;he precipitate by decantation with a small quantity of water, 5 to 10 cc. at a 
ime, adding the washing to the filtrate until it is about three times the original 
volume. 


I. . 


I Precipitate.—White—contains AgCl, 

E tfgCl, PbCl 2 . 

Add 15 to 20 cc. of hot water and 
fi iour repeatedly through filter while _ 
jiot; heat if necessary. Wash the residue 
nsure complete solution of PbCl 2 . 


Filtrate.—Contains ions of the 
following groups. Set aside for 
subsequent analysis. 


with additional fresh hot water to 


-II. 


Residue.—AgCl, 

»gCi. 

i! Pour 10-15 cc. 


MH 4 OH repeatedly 
r| through filter paper, 
\ containing the resi¬ 
ts due to insure the 
' solution of AgCl. 

IV. 


Filtrate.—Pb+ + Cl 2 -i (if allowed to cool, needle-like 
crystals will be deposited = PbCl 2 ). 

Divide the hot solution in two portions. 


(a) To the 
smaller portion 
add K 2 Cr 2 C >7 or 
K 2 Cr0 4 . A yellow 
ppt. is PbCr0 4 , 
soluble in NaOH. 


(6) To the larger cooled portion 
add one-fifth of its volume of H 2 S0 4 
cone. Cool, shake, and allow to stand 
5 min. 


Ppt. PbS0 4 , white, solu¬ 
ble in NaOH, NH 4 C 2 H 3 0 2 
solutions. Reprecipi¬ 
tated from the latter by 
HC 2 H 3 0 2 + K 2 Cr0 4 as yel¬ 
low PbCr0 4 . 


Fil. 
Tl. pptd. 
by KI as 
yellow 
TIL 


Residue.—HgNH 2 Cl+Hg, black. 

Confirm as follows: tear off a portion of the 
filter containing the residue, drop into a test tube, 
and add a few drops of aqua regia. Warm, 
dilute, and filter. 

The filtrate contains Hg+ + Cl 2 -. Boil the solu¬ 
tion to destroy the excess of aqua regia and add 
SnCl 2 ; a white ppt. of HgCl or a gray ppt. 
HgCl+Hg proves the presence of mercury. 


Filtrate.—Ag( NH 3 ) 2 +Cl - 
Acidify with dil. HNO 3 — 
a white ppt. is AgCl. 

AgCl fused on charcoal 
with Na 2 C0 3 in reducing 
flame yields metallic silver. 


The rarer metals are precipitated by HC1 as follows: W as H 2 W0 4 -H 2 0, 
white; Tl as T1C1 3 , white; Ta as HTa0 3 , white; Mo as H 2 Mo0 4 , white; Te as 
H 2 Te0 3 , white, Ta, Tl, and Te classified also in later groups 
KC10 3 +HC1 may be used in place of aqua regia. Boil ott Cl. 

































42 


QUALITATIVE ANALYSIS 


Notes on the Separation of the Hydrogen Chloride Group 

i 

I. The addition of HC1 to alkaline solutions may precipitate members 
of other groups, for example, arsenic (yellow), antimony (orange), and tic 
(brown). All such precipitates must be dissolved before undertaking furthei 
analysis. (See Preparation of Solutions, Part IV.) L 

White BiOCl and SbOCl may precipitate, but the addition of HC1 wil 
cause these to dissolve. In concentrated solutions NaCl, BaClj, etc., may b( 
precipitated. These dissolve on dilution. 

Precautions.—Sufficient IIC1 should be added to precipitate all the silver, 
mercury, and lead. It is well to allow the precipitate to settle and add s 
drop or so of the reagent to see whether the precipitation is complete or tc 
test the filtrate for members of the group. This precaution should be observed . 
in the analysis of the subsequent groups, as insufficient group reagents will B 
cause considerable difficulty later and erroneous interpretations, owing tc 
metals passing into groups to which they do not belong. A large excess ol 
HC1 should be avoided on account of the solubility of the chlorides in HC1 
PbClj is slightly soluble in cold water, causing it to pass into the the sub¬ 
sequent group, where it precipitates as PbS. 

The precipitate is washed to insure the removal of other salts that may be 
carried down by the chlorides. 

If silver has not been completely removed it may be detected in the filtrate 
by passing in H 2 S 


AgN0 3 +H 2 S = 2HN0 3 + | Ag 2 S black. 

The sulphide is insoluble in alkali hydroxides and sulphides, but dissolves 
in hot dilute nitric acid. 


3Ag 2 S -f 8HN0 3 = 6AgN 0 3 +2NO -f 4H 2 0+ 3S. 

II. Lead chloride dissolves slowly, hence the precipitate 
washed with hot water. 


re 



peatedly 


III. Turbidity, resulting upon the addition of NH 4 OH to the residue 
left after the removal of lead, is generally caused by the precipitation of the 
white basic salt of lead Pb(OH)Cl, due to the incomplete removal of lead 
through insufficient washing of the combined chlorides with hot water. The 
presence of lead chloride, however, does not interfere with the tests for mercury 
as the lead salt dissolves in HN0 3 . 

In the test for lead either method is sufficient proof of its presence. 

IV. The change of color of the white residue to black is a characteristic 
reaction of mercurous chloride. The confirmatory test is made in case oi 
doubt where the discoloration is not decided. 





THE METALS 


43 


The precipitation of AgCl from its ammonium solution by dilute nitric 
,cid is a sufficient confirmation of its presence. 

Metallic mercury reduces AgCl to metallic silver: 

Hg+2 AgCl = HgCl 2 +2 Ag 

rhe silver thus reduced does not dissolve in NH 4 OH but remains with the 
aercury precipitate. If the quantity of mercury is large and that of silver 
elatively small, all of the silver will remain with the mercury precipitate 
o that the ammonia extract will fail to show the presence of silver. In 
ase a large black residue remains after the ammonia treatment, dissolve 
he residue in aqua regia, dilute with water, filter and test the residue on the 
ilter for silver, by extracting with ammonia and acidfying the extract with 
litric acid as directed. 


44 


QUALITATIVE ANALYSIS 


CLASSROOM REVIEW 


1. Turn to the Comparative Tables, Part V, and study the reaction: 
indicated under Hydrogen Chloride Group. From the insolubilities devise 
a plan other than the one given, for the separation of the members of thi: 
group. 

2. Name the metals of the Hydrogen Chloride Group. Why are the} 
classed together? 

3. Does the group precipitant throw out all the members of the group 
completely? 

4. Does the absence of a precipitate prove the absence of all the metah 
of this group? 

5. Does the precipitate always indicate the presence of the silver group? 

6. What would be the result if HC1 were added to a hot solution con 
taining the members of this group? 

7. If AgCl were not all dissolved by the NH 4 OII treatment where woulc 
it appear later? How would its presence be proved in the mercury residue' 
Why does mercury prevent the complete extraction of AgCl by NH 4 OH? 

8. Why should the aqua regia be destroyed before testing for mercurj 
with SnCL? 

9. If the ammonia solution of silver is turbid, what is the cause? 

10. Explain the reaction of NH 4 OH with AgCl. 

11. Why are precipitates washed? 

12. Account for the facts that lead and mercury appear in the following 
group. 

13. How would you distinguish corrosive sublimate (HgCl 2 ) from calome 
(HgCl)? 

14. If the solution to be tested is alkaline, would acidification with H 2 SO 
do as well as HNO s ? 

15. How would metallic silver be distinguished from metallic lead? 

16. If considerable matter remained, after an attempt to dissolve t 
substance for a qualitative examination, how would you prove that some o: 
the substance had dissolved? 

17. How can you distinguish between the chlorides of lead, mercury 
and silver? 

18. Write the reactions that take place when: (a) HC1 is added to 
AgNO s . Pb(N0 3 ) 2 , HgNCL. ( b) HgCl+aq. reg. (c) NH 4 OH added tc 
AgCl, HgCl, PbCl 2 . ( d ) PbCl 2 +H 2 S04. ( e ) PbCla-fK^CrCL. 






HYDROGEN SULPHIDE GROUP 

Copper and Tin Groups, Group 2 

DESCRIPTIVE 

Common Metals. — Sulphides insoluble in (NHJzSx —Bismuth, Cadmium. 
Copper, Lead, Mercury. 

Sulphides soluble in ( NHi) 2 S x —Antimony, Arsenic, Tin, Gold, Platinum. 

Rare Metals. — Sulphides, insoluble —Osmium, Palladium, Rhodium, 
Ruthenium. 

Sulphides, soluble —Iridium, Molybdenum, Selenium, Tellurium, Tungsten. 
General Characteristics. 

The members of this group, though widely scattered in the 
periodic system of classification, are grouped together qualita¬ 
tively on account of the insolubility of their sulphides in dilute 
acids. They subdivide into two groups—metals whose sulphides 
are insoluble in ammonium sulphide or polysulphide, and metals 
whose sulphides are soluble in these reagents. These subdivisions 
are frequently spoken of as the Copper and Tin Groups; we will 
speak of them as the Soluble and Insoluble H 2 S Subgroups, A 
and B. 

THE INSOLUBLE H 2 S SUBGROUP—A (COPPER GROUP) 

The sulphides of this subgroup are insoluble in yellow ammonium sulphide. 
Individual Characteristics. 

Lead. —Its slight solubility as a chloride causes a small amount to pass 
into this group. The metal has been taken up in the previous group. 

Mercury is bivalent in this group. Its characteristics have already been 
discussed. 

BISMUTH 

Bi, fttwt. 208.0; sp.gr. 9.747; m.p. 271° C.; b.p. 1420° C.; oxides, Bi 2 0 3 , Bi 2 0 6 . 

Bismuth is a reddish white metal. It is exceedingly brittle and easily 
powdered. The element is a poor conductor of heat and electricity. It has 

45 


46 


QUALITATIVE ANALYSIS 


a low melting-point (271° C.) hence can be easily melted in the Bunsen flame. 
The metal possesses the peculiar property of expanding when the molten 
mass solidifies and cools, the expansion taking place after solidification. ; 
Bismuth is the most diagmagnetic substance known. It occupies an extreme 
place in the thermo-electric series and is used with antimony in the prepara¬ 
tion of delicate thermopiles. 

Nitric acid is the best solvent of bismuth. Although it is soluble in hot 
sulphuric acid, it is only very slightly soluble in the cold acid. The element 
is practically insoluble in hydrochloric acid, but readily dissolves in nitro- 
hydrochloric acid. The hydroxides, oxides, and most of the bismuth salts I 
are readily soluble in hydrochloric, nitric, and sulphuric acids. 

The salts of bismuth in solution on dilution, give a white precipitate of j 
basic salt, which is insoluble in tartaric acid and blackens with H 2 S (distinction 
from antimony). A list of the more common compounds may be found in 
Part V. 



DETECTION 


General Procedure.—Bismuth is precipitated from its solution, contain- 
ing free acid, by H 2 S gas, as a brown sulphide, Bi 2 S 3 . The compound is 
insoluble in ammonium sulphide (separation from arsenic, antimony, and 
tin), but dissolves in hot dilute nitric acid (separation from mercury). The 
nitrate, treated with sulphuric acid and taken to SO 3 fumes, is converted to 
the sulphate and dissolves upon dilution with water (lead remains insoluble 
as PbS0 4 ). Bismuth is precipitated from this solution by addition of 1 
ammonium hydroxide, white Bi(OH ) 3 being formed (copper and cadmium 
dissolve). If this hydroxide is dissolved with hydrochloric acid and then 
diluted with a large volume of water, the white, basic salt of bismuth oxy¬ 
chloride, BiOCl, is precipitated. The compound dissolves if sufficient hydro¬ 
chloric acid is present. It is insoluble in tartaric acid (distinction from 
antimony). 

Reducing Agents.—Formaldehyde in alkaline solution, hypophosphorous 
acid, potassium or sodium stannite, reduce bismuth compounds to the metallic 
state. For example, a hot solution of sodium stannite poured onto the white 
precipitate of Bi(OH ) 3 on the filter will give a black stain. The test is very 
delicate and enables the detection of small amounts of the compound. 

3K 2 SnO 2 -f 2BiCl 3 -f 6KOH = 2 Bi -f 3K 2 SnO 3 -f 6KC1+3H 2 0 

Blowpipe Test.—A compound of bismuth heated on charcoal with a 
powdered mixture of carbon, potassium iodide and sulphur, will give a scarlet 
incrustation on the charcoal. 






THE METALS 


47 


CADMIUM 

Cd, at.wt. 112.4; sp.gr. 8.642; m.p. 320.9° C.; b.p. 778° C.; oxide, CdO 

Cadmium is a bright silvery metal of faint bluish tinge. Like lead it 
produces a metallic streak on paper, but not so readily. The metal is harder 
and more tenacious than tin and is ductile and malleable. Heated to 80° C. 
it becomes brittle and may be powdered in a mortar. It crackles like tin 
when bent on account of its crystalline structure. It has a comparatively 
low melting-point (320.9° C.), when heated in air it burns, evolving brown 
fumes of the oxide. 

Cadmium is slowly soluble in hot, moderately dilute hydrochloric acid 
and in sulphuric acid, much more readily in nitric acid. It is soluble in 
ammonium nitrate. The oxide is readily soluble in acids. 

The salts of cadmium, generally, are but slightly dissociated in solution, 
hence are liable to be incompletely precipitated by reagents. A list of the 
more common salts is given in Part V. 

DETECTION 

General Procedure.—Cadmium is precipitated by hydrogen sulphide 
from an acid solution as yellow cadmium sulphide, CdS. The precipitate is 
insoluble in ammonium sulphide (distinction from arsenic, antimony, and 
tin), but dissolves upon addition of hot nitric acid (separation from mercury). 
Upon addition of sulphuric acid and explusion of nitric by taking the solu¬ 
tion to SO 3 fumes, and dilution with water, cadmium remains in solution 
(lead is precipitated, PbSO<). Bismuth is precipitated by ammonium hydrox¬ 
ide and removed by filtration. Potassium cyanide is added to prevent the 
precipitation of copper sulphide; and hydrogen sulphide is led into the 
solution, whereupon cadmium precipitates as yellow CdS. 

Spectrum. —Cadmium gives a brilliant spectrum of green and blue lines. 

Blowpipe Tests.—Heated on charcoal in the reducing flame, cadmium 
gives a brown incrustation. The residue is volatile in the reducing flame. 


COPPER 

Cu, at.wt. 63.67; sp.gr. 8.89 20 °; m.p. 1083° C. (in air 1066); b.p. 2310° C.; 
oxides Cu 2 0 and CuO 

The reddish (salmon red) ductile and malleable metal is an excellent 
conductor of heat and electricity. It possesses a bright metallic lustre when 
freshly cut but soon tarnishes. It is not acted on by dry air under ordinary 




48 


QUALITATIVE ANALYSIS 


conditions. The basic carbonate, verdigris (CuC0 3 • Cu(OH) 2 ) is formed in 
moist air. Copper heated in the air is coated with black cupric oxide. 

The metal is insoluble in HC1 and in dilute H 2 S0 4 (see Electromotive 
series) but dissolves in concentrated H 2 S0 4 , and in dilute HN0 3 . It is pre¬ 
cipitated from solutions of its salts by metals nearer sodium in the electro¬ 
motive series. 

The element has two valences, hence forms two series of salts, cuprous 
and cupric (see list in Part V). The copper ions of the bivalent form are 
blue, the monovalent ions are colorless. 

DETECTION 

General Procedure.—Copper is precipitated in an acid solution by H 2 S 
gas, along with the other members of the hydrogen sulphide group. The 
insolubility of its sulphide in sodium sulphide is a means of separating copper 
from arsenic, antimony, and tin. The sulphide dissolves in nitric acid 
(separation from mercury) along with lead, bismuth, and cadmium. Lead 
is precipitated as PbS0 4 by sulphuric acid, and bismuth is precipitated as 
Bi(OH) 3 , ammonium hydroxide. Copper passes into the filtrate, coloring this 
solution blue. 

Flame Test.—Substances containing copper (sulphides oxidized by 
roasting), when moistened with hydrochloric acid and heated on a platinum 
wire in the flame, give a blue color in the reducing flame and a green tinge to 
the oxidizing flame. 

Wet Tests.—Nitric acid dissolves the metal or the oxides (sulphides should 
be roasted), forming a green or bluish-green solution. Ammonium hydroxide 
added to this solution will precipitate a pale blue compound, which dissolves 
in excess with the formation of a blue solution. (Nickel also gives a blue 
color.) 

Hydrogen sulphide, H 2 S, passed into an acid solution containing copper, 
precipitates a brownish-black sulphide, CuS. (Distinction from nickel.) 

Copper is displaced from its solution by zinc, cadmium, tin, aluminum , lead, 
bismuth, iron, cobalt, nickel, and magnesium. If a strip of iron is placed 
in a solution of copper, neutral or slightly acid, it will be coated over with 
metallic copper. (Delicacy 1 part Cu per 120,000 of solution.) 

The greenish-blue cupric salts in acid solution are reduced to the colorless 
cuprous compounds by metallic copper and by stannous chloride and by 
arsenious acid, grape sugar, sulphurous acid in alkaline solutions. 

Potassium Ferrocyanide precipitates reddish brown cupric ferrocyanide 
insoluble in dilute acids, soluble in NH 4 OH. 1 part Cu may be detected 
in 200,000 parts of water, the solution appearing reddish brown. 








THE METALS 


49 


THE SOLUBLE H 2 S SUBGROUP—B (TIN GROUP) 

The sulphides of this subgroup are soluble in yellow ammonium sulphide. 

Individual Charateristics. 

ANTIMONY 

Sbj at.wt. 120.2; sp.gr. 6.62; m.p. 620° C.; 1440° C.; oxides, Sb 2 0 3 , 

SbO<, Sb 2 O s . 

Antimony as it ordinarily occurs is a lustrous, bluish white metal with 
granular or coarsely laminated structure according as it is quickly or slowly 
cooled. It is brittle and may be readily powdered in a mortar. It is a poor 
conductor of heat and electricity. The metal has two amorphous forms, 
one form is soluble in CS 2 , the other is an unstable variety which easily 
changes to the crystalline form by heat or by being scratched or struck. The 
metal is not affected by air at ordinary temperatures, but burns at red heat 
with formation of white Sb 2 (> 3 . Like bismuth antimony expands on solidi¬ 
fication. It is oxidized by nitric acid, dilute HN0 3 producing principally 
Sb 2 0 3 and concentrated HN0 3 , the pentoxide Sb 2 0 5 . Antimony combines 
directly with the halogens with evolution of light and heat. It unites with 
metals and forms a number of useful alloys. Antimony generally increases 
the fusibility, brittleness and hardness of the metals with which it is com¬ 
bined, and imparts the property of expanding on solidfication—an important 
factor for castings. 

Metallic antimony is practically insoluble in cold dilute hydrochloric, 
nitric or sulphuric acid and the oxides, Sb 2 0 3 or Sb 2 0 6 , are precipitated in 
strong nitric acid. The element, however, is readily soluble in hydrochloric 
acid containing an oxidizing agent, such as nitric acid, potassium chlorate, 
chlorine, bromine, etc. The oxides of antimony are soluble in hydrochloric 
acid and the caustic alkalies. 

Most of the salts in solution precipitate basic salts when diluted with 
water. Tartaric acid prevents precipitation (see Detection). A list of 
antimony compounds is given in Part V. 

DETECTION 

Hydrogen Sulphide precipitates the orange-colored sulphide of antimony 
from fairly strong hydrochloric acid solutions (1 :4) in which several mem¬ 
bers of the group remain dissolved. Arsenic is also precipitated. The latter 
may be removed by boiling the solution containing the trichloride, AsCl* 
being volatile. 






50 


QUALITATIVE ANALYSIS 


General Procedure.—If antimony is already present as a sulphide, 
together with other elements of the hydrogen sulphide group, it may be 
dissolved out by treating the precipitate with sodium hydroxide or potassium 
hydroxide or sodium sulphide or ammonium polysulphide. Antimony sul¬ 
phide is precipitated upon acidifying the filtrate. Arsenic and tin will also be 
precipitated with antimony if they are present in the original precipitate. 
Should a separation be necessary, the precipitate is dissolved with hot con¬ 
centrated hydrochloric acid, with the addition of crystals of potassium chlorate, 
from time to time, until the sulphides dissolve. The solution is placed in a 
Marsh apparatus, pure zinc added and the evolved gases passed into a neutral 
solution of silver nitrate. The black precipitate of silver antimonide and 
metallic silver are filtered off, washed free of arsenous acid, and the antimonide 
dissolved in strong hydrochloric acid (silver remains insoluble). The orange- 
colored antimony sulphide may now be precipitated by diluting the solution 
with water and passing in H 3 S gas to saturation. See also page 78. 

Minerals which contain antimony, when heated alone or with 3 to 4 parts 
of fusion mixture (K 2 C0 3 and Na 2 C0 3 ), on charcoal, yield dense white fumes, I 
a portion of the oxide remaining as a white incrustation on the charcoal. A 
drop of ammonium sulphide placed upon this sublimate gives a deep orange 
6tain. 

Hydrolysis.—Most of the inorganic antimony salts are decomposed by 
water, forming insoluble basic salts, which in turn break down to the oxide of 
antimony and free acid. An excess of tartaric acid prevents this precipitation. 
(Distinction from bismuth.) 

Distinction between Antimonous and Antimonic Salts. 

Chromates form with antimonous salts green chromic salts and antimonic 
salts. 

Potassium Iodide reduces antimonic salts, free iodine being liberated. 

Traces of Antimony.—Nascent hydrogen liberated by the action of zinc 
and hydrochloric or sulphuric acid reacts upon antimony compounds with the 
formation of stibine. This gas produces a black stain on mercuric chloride or 
silver nitrate paper. 

Comparison of the Marsh Tests for Antimony and Arsenic 

Stibine and arsine are formed by the reduction of compounds of the cor¬ 
responding elements by nascent hydrogen; both leave a deposit in the form 
of a black mirror on a cold white surface when the flames of the ignited gases 
impinge against the cold body. The stain of arsenic, however, is soluble 
in a hypochlorite solution, while that of antimony is not. Arsine passed 
through a solution of AgN0 3 will reduce the compound, forming black flakes 










THE METALS 


51 


, metallic silver. Stibine does not reduce silver nitrate, but precipitates 
1 black silver antimonide. The arsenic mirror, dissolved in a drop of HNOs 
then evaporated to dryness and the residue moistened with a drop of silver 
nitrate, gives a brick-red color. Antimony remains colorless. The spot 
dissolved in ammonium sulphide and evaporated to dryness yields a bright 
yellow residue. Antimony residue is orange-red. If arsine is conducted 
through a hard glass tube with a constriction, and this portion of the tube is 
heated, an arsenic mirror forms in advance of the flame. Stibine decomposes, 
depositing antimony immediately above the flame, since antimony is less 
volatile. 


As i at.wt.74.96- 


ARSENIC 

cryst. 6.73 

’amorp. sp ' gr ‘ 4.72 m,p ‘ 
Oxides, Asj0 3 , As 2 0 6 


860 subl. 664° 
... p * <360° 


Arsenic is a brittle steel gray, crystalline metal. It is a good conductor 
of electricity, and is odorless and tasteless. It is volatile at temperatures 
above 100°, and is vaporized rapidly at a dull red heat. The vapor is yellow 
and has the odor of garlic. When heated in air arsenic burns with a bluish 
flame, forming arsenous oxide, As 2 0 3 . It combines in powdered form with 
chlorine, forming AsClj. With heat it combines with Br, I, and S. Arsenic 
is a constituent of many alloys. 

The metal dissolved in dilute HNO s forms arsenous acid, in concentrated 
HN0 3 arsenic acid. Arsenic occurs in nature in crystalline masses. 

Solubility.—The oxide, As 2 0 3 , is not readily acted upon by dilute acids— 
hydrochloric or sulphuric. The compound is soluble, however, in alkaline 
hydroxides and carbonates. Nitric acid oxidizes As 2 0 3 to the higher oxide, 
AS 2 O 5 , which is soluble in water. The sulphides As 2 S 3 and As 2 S 5 are prac¬ 
tically insoluble in hydrochloric or sulphuric acids, but are dissolved by the 
fixed alkalies and alkali sulphides. All arsenites, with the exception of the 
alkali arsenites, require acids to effect solution. 


DETECTION 

Hydrogen sulphide precipitates the yellow sulphide of arsenic, As 2 S 3 , when 
passed into its solution made strongly acid with hydrochloric acid. If the 
solution contains more than 25 per cent hydrochloric acid (sp.gr. 1.126) the 
other members of the hydrogen sulphide group do not interfere, as they are 
not precipitated from strong acid solutions by hydrogen sulphide. Arsenic 
sulphide is soluble in alkaline carbonates. (Antimony sulphide, Sb»Sj, 
reddish yellow, is insoluble in alkaline carbonates.) 




52 


QUALITATIVE ANALYSIS 




Tube containing sensitized 
mercuric chloride paper 
4mm bore. 


Rubber stopper. 


Volatility of the chloride, AsC 1 3 , is a means of separation and distinctioi 
of arsenic. The compound is distilled from a concentrated hydrochloric acic 

solution, assisted by a stream of HC1 gas 
which separates it from other elements 
Arsenic must be in the trivalent form. 

Blowpipe.—The oxide or sulphide 
mixed with NajCO s and placed on char¬ 
coal heated by the blowpipe gives a filn 
which is volatile and has a garlic odor. 

Open Tube Test.—Arsenic mixed with 
charcoal and heated in an open tube vola¬ 
tilizes and forms a film of As 2 0 3 on the 
cool part of the tube. 

Flame Test.—Pale azure blue. 
Ammonium molybdate solution heated 
to 50°-G0° with arsenic compounds gives 
a crystalline yellow precipitate—ammo-1 
nium arsenomolybdate. A few drops of 
nitric acid aid the reaction. The solu¬ 
tion must be concentrated. Add a few 
drops of the arsenic compound to a test 
tube half full of ammonium molybdate 
containing nitric acid. 

Distinction between Arsenates and 
Arsenites.—Magnesia mixture precipitates 
white MgNELAsCL, when added to ammo- 
niacal solutions containing arsenates, but 
it produces no precipitate with arsenites. 

Red silver arsenate and yellow silver 
arsenite are precipitated from neutral solu¬ 
tions by ammoniacal silver nitrate. An 
arsenate gives a yellow precipitate with 
ammonium molybdate solution. 


Tube containing glass wool 
moistened with lead acetato 
solution. 


T lubber stopper. 


Dry lead acetate paper to 
absorb traces of H 2 S. 


Rubber stopper. 


^ 5<kc;.C3 »ob^ 

^T5rC7CHE 

“difcacid 


4 ounce bottle with 
solution containing 
E£§ sample + H 2 S0 4 (1-4) 
ordil. HC1. 


OOOO O 6 O O 

yoAOAO.oo Zinc shot> 


Traces of Arsenic 


o o o o o o o o 


Fig. 13. —Modified Gutzeit 
Apparatus. 


The Gutzeit Test.—The reaction de¬ 
pends upon the principle that arsine is 
formed when arsenic compounds are heated 
in a test tube with pure zinc and a caustic 
alkali or an acid. Filter paper moistened with mercuric chloride held in the 
fumes of arsine will be turned yellow, deepening to a brown or black. 




























THE METALS 


53 


Modified Gutzeit Method.—An excellent form of apparatus for detecting 
small amounts of arsenic by the Gutzeit method is shown in Fig. 13. By 
this means less than O.OOOOOlg. of arsenic may be detected. The arsenic 
solution containing a small amount of iron is acidified with dilute HjSCL-fNaCl, 
the iron and arsenic are reduced with a few drops of strong SnCL solution 
and the mixture poured into a 60 cc. bottle, arsenic-free zinc shot is added 
and the apparatus quickly connected. Arsine produces a black stain on 
the HgCla paper, the length of the stain determining the amount of arsenic 
present. 

H 2 S should be removed by boiling the acid solution and by subsequent 
oxidation with a few drops of KMn0 4 solution. Antimony, if present in 
large amount, will also produce a stain, but ordinarily does not interfere. 

Marsh Test.—This test depends upon the formation of arsine by the reduc¬ 
tion of arsenious or arsenic compounds by nascent hydrogen (H+catalyzer). 



The generator consists of a 250 cc. flat-bottomed flask in which zinc is placed. 
A thistle tube passes through a two-holed rubber stopper to the bottom of the 
flask. A hard glass tube, drawn out to capillarity at one end, with two 
constrictions near the middle, is connected to the flask by means of a second 
tube, a tube containing CaCl 2 being inserted. See illustration. The genera¬ 
tor is started by pouring dilute sulphuric acid, which is free from arsenic, 
through the thistle tube on to the arsenic-free zinc. A little copper sulphate 
will start the reaction. When the air is expelled, light the issuing gas; then 
pour in the solution to be examined through the thistle tube. If arsenic is 
present, the flame will soon be colored a lilac hue by the arsine. If a cold 
porcelain evaporating dish is depressed over this flame, a spot of metallic 
arsenic will deposit upon it. This spot will dissolve upon the addition of 































54 


QUALITATIVE ANALYSIS 


sodium hypochlorite or bleaching powder solutions. Antimony acts very 
similarly—stibine is formed by the action of nascent hydrogen. The anti¬ 
mony stain is not soluble in sodium hypochlorite. See comparison of the 
Marsh Test for Antimony and Arsneic. 

Gatehouse Test.—Differs only from the above in the materials used for 
generating hydrogen. This is produced by the action of KOH on Al. 

Fleitmann Test.—KOH or NaOH on Zn used for generating H. 

Bettendorff Test.—When a mixture of equal parts of cone. HC1 and cone. 
SnCl 2 with one part of water is boiled with a few drops of H 3 As0 3 or H 3 AsO<, 
the solution darkens, due to the reduction of arsenic to the metallic state. 

Reinsch’s Test.—If a strip of pure copper foil is introduced into a solution 
containing arsenic acidulated with HC1 and the mixture boiled, the copper will 
be coated with a gray stain. Antimony and organic matter will do the same. 
If the copper foil is removed and dried between folds of filter paper, the foil then 
rolled into a small coil and dropped into a clean, hard glass tube, then heated, 
arsenic will volatilize and collect in the cooler portion of the tube in the form 
of white octohedral crystals of As 2 0 3 . Organic matter burns away. Anti¬ 
mony deposits in an amorphous form or in acicular crystals. Mercury, which 
may also coat the foil, volatilizes and collects in the cooler portion of the 
tube in fine globules of metallic mercury. 

TIN 

Sn, at.wt. 118.7; sp.gr. 6.66; m.p. 232° C.; b.p. 2276° C.; oxides Sn0 2 , SnO 

Tin is a silver white, lustrous, crystalline, soft, malleable metal. It is 
inferior in ductility and tenacity to most of the useful metals, though superior 
to lead. The metal is not oxidized by air at ordinary temperatures. Tin 
forms a part of several important alloys, bronze, pewter, Britannia metal. 
It is used for coating over metals to protect them from corrosion. Tin at 
red heat decomposes water. The metal is divalent and tetravalent, hence 
has two senes of compounds. A list of the important compounds may be 
found in Part V. 

Tin is soluble in HC1 and in dilute H 2 S0 4 . It dissolves in aqua regia 
and in hot NaOH and KOH. It is converted to the insoluble metastannic 
acid by HNO*. 

DETECTION 

General Procedure.—Tin is separated, together with arsenic, antimony, 
gold and platinum, from the hydrogen sulphide precipitate of the metals 
of the second group, by the action of yellow ammonium sulphide. (Normal 
ammonium sulphide does not readily dissolve the sulphides of tin.) If the 




THE METALS 


55 


ammonium sulphide solution is acidulated with hydrochloric acid and the 
acid solution reduced with iron, antimony, arsenic, platinum and gold are 
precipitated in the metallic form. The presence of tin, which is present as 
stannous chloride, is indicated by the reducing action of the solution on 
mercuric chloride, a white precipitate of HgCl or a gray precipitate of Hg 
being thrown down. 

The hydrochloric acid solution of the sample is reduced by means of a 
small piece of iron wire and treated with an excess of cold potassium hydroxide. 
The solution is filtered if not clear and an ammoniacal solution of silver nitrate 
added (one part AgN0 3 : 16 parts NH 4 OH). A brown precipitate of metallic 
silver indicates the presence of tin. Antimony, arsenic, platinum and gold 
are precipitated by the iron, while all of the heavy metals remaining, except 
lead, tin, aluminum, chromium, and zinc, are removed by the treatment 
with potassium hydrate. 

Welch and Weber recommend the following method for detection of tin: 
Ten cc. of concentrated hydrochloric acid are added to the superficially dried 
precipitated sulphides from the ammonium sulphide separation. Arsenic, 
which does not decompose, is filtered off and the filtrate diluted to 70 cc. 
volume, then saturated with H 2 S, and heated to expel excess H 2 S. Five cc. 
of hydrogen peroxide are added, and the mixture heated until the precipitate 
is redissolved. Five to 10 grams of oxalic acid are added and H 2 S passed 
into the hot solution. Antimony separates as a red sulphide. The filtate 
contains the tin. Test lead is added and then mercuric chloride. White or 
grayish precipitate indicates presence of tin. 



56 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 
Chemical Reactions 

Insoluble H 2 S Subgroup A (Copper Group) 

The elements will be studied in the order in which their 
isolation is accomplished in the general procedure for separation 
of the members of the group. 

Mercuric mercury, Hg ++ , use a solution of mercuric chloride. 

1/Add 1 cc. HC1 (1.12) and dilute to 10 cc. Warm and pass 
in H 2 S slowly, and note the colors of the precipitates formed. 

Reactions.— 3HgCl 2 +2H 2 S = HgCl 2 • 2HgS+4HC1 

HgCl 2 • 2HgS+H 2 S = | 3HgS+2HCl 

2 . Allow to settle, and wash by decantation. Test the solu¬ 
bility of the precipitate in HNO3 (1 vol. HNO 3 (sp.gr. 1 . 2 ) to 
2 vols. H 2 0). 

3. Test the solubility of HgS in (NH 4 ) 2 S X solution . 1 

4. Pour off the acid and wash by decantation and test the solu¬ 
bility in Br water (warm) or in boiling aqua regia. The precipi¬ 
tate dissolves. 

5. Boil the solution to drive off chlorine. Cool and add SnCk; 
the white or gray precipitate is HgCl+Hg. 

LEAD 

Use a solution of lead acetate. 

6 . Add 2 cc. HC1, warm and pass in H 2 S, noting the color of the 
precipitate formed (PbS). 


Reaction.— Pb(C 2 H 3 0 2 ) 2 +H 2 S = j PbS+2HC 2 H 3 0 2 . 

7. Allow to settle and wash by decantation. Boil precipitate 
in a casserole with 4 cc. HNO 3 (see above). 

Reaction.—3PbS+8HN0 3 = 3Pb(N0 3 ) 2 + | 2N0+4H 2 0 + j 3S. 

1 The precipitate HgS dissolves in Na 2 S+NaOH. 


THE METALS 


57 


8. To the solution formed add a few drops of dilute H2SO4; 
the white precipitate is PbSC>4. 

Reaction.—Pb(N0 3 ) 2 +H 2 S0 4 = I PbS0 4 +2HN0 3 . 

Boil until white fumes appear, and dilute. Does the pre¬ 
cipitate seem to have increased? 

9. Dissolve in NH 4 C 2 H 3 O 2 and add K 2 CrC> 4 . Does the pre¬ 
cipitate dissolve when acetic acid is added? Try it. 

Reaction.—Pb(C 2 H o 0 2 ) 2 +K 2 Cr0 4 = | PbCr0 4 -f 2KC 2 H 3 0 2 . 

10. Take 2 cc. of BaCl 2 and add a few drops of H2SO4. 

Reaction.—BaCl 2 +H 2 S0 4 = J. BaS0 4 -f-2HCl. 

11. Test the solubility of the white BaSCU in NH 4 C 2 H 3 O 2 . 

12. Next add a little K 2 Cr 04 to 2 cc. BiCl 3 . Test the solu¬ 
bility of (Bi 0 ) 2 Cr 04 in acetic acid. What conclusion do you 
draw from these tests? 


BISMUTH 

Use solution of bismuth chloride. 

13. Add 1 cc. HC1 and dilute to 10 cc. A precipitate of 
BiOCl forms with greater dilution. Try it. 

14. Warm and pass in H 2 S. 

Note the color of Bi 2 S 3 . 

Reaction.—2BiCl 3 +3H 2 S = | Bi 2 S 3 +6HCl. 

15. Test the solubility of Bi 2 S 3 in (NKU^S* solution. Allow 
to settle, decant and wash once by decantation. Boil the precipi¬ 
tate with 1 cc. of HNO3. 

Reaction.—Bi 2 S 3 +8HN0 3 = j 2Bi(N0 3 ) 3 + T 2N0+4H 2 0 + j 3S. 

16. To the solution of Bi(NOs )3 add a few drops of H 2 S0 4 . . 
Does a precipitate form? 


58 QUALITATIVE ANALYSIS 

17. Add NH 4 OH until alkaline; note the color of the precipi¬ 
tate Bi(OH) 3 . 

Reaction.—Bi(N0 3 ) 3 -|-3NH 4 0H = J. Bi(0H) 3 +3NH 4 N0 3 . 

18. Does the precipitate dissolve in an excess of NH 4 OH? 
Filter and wash once. Dissolve in a few drops of HC1 and pour 
the solution into a second test tube containing 15 to 20 cc. of 
water. Precipitate is BiOCl. 

Reaction.—BiCl 3 +H 2 0= 1 BiOCl+2HCl. 

19. Filter and add a fresh solution of sodium stannite 
(NaOH-f-SnCk); the black precipitate is metallic bismuth. 

Reaction.— 

2Bi0Cl+3Na 2 Sn0 2 +2Na0H=3Na 2 Sn0 3 +2NaCl+H 2 0 + j 2Bi 
COPPER 

Use a solution of copper sulphate. 

20. Add 1 cc. HC1 and dilute to 10 cc. Warm and pass in 
H 2 S; note the color of the precipitate, CuS. 

Reaction.— CuS0 4 +H 2 S = CuS+H 2 S0 4 . 

21. Test the solubility of CuS in (NFLO 2 SX solution. 

22. Wash by decantation, dissolve in 1 cc. HNO 3 , dilute, and 
add two or three drops of H2SO4. Does a precipitate form? 

23. Boil until white fumes appear, and again dilute. Is there 
a precipitate now? 

Reaction.— 3CuS+8HN0 3 =3Cu(N0 3 ) 2 + T 2N0+4II 2 0 + 1 3S. 

Cu(N0 3 ) 2 +H 2 S0 4 = CuS 0 4 + t 2HN0 3 . 

24. Make alkaline with NH 4 OH. Note that the light-blue 
precipitate, formed in a drop or so of ammonia, dissolves in an ex¬ 
cess of that reagent and forms a deep blue solution (Cu(NH 3)4 
ion). 

Reaction.— CuS0 4 +2NH 4 0H= j Cu(0H) 2 + (NH 4 ) 2 S0 4 . 

Cu (OH) 2 +(NH 4 ) 2 SO 4 -f2NH 3 = Cu (NH 3 ) 4 S0 4 +2H 2 0. 


THE METALS 


59 


25. Divide the solution into two portions. To one, acidified 
with acetic acid, add K 4 Fe(CN) 6 . Note the color of the precipi¬ 
tate Cu 2 Fe(CN )6 by pouring on filter paper. 

Reaction.—2CuSO 4 +K 4 Fe(CN) 6 = f Cu 2 Fe(CN) 3 +2K 2 S0 4 . 

26. To the other portion add solid KCN until the color dis¬ 
appears. Now pass in H 2 S. Does a precipitate form? 

Deep blue 

Reaction.—2 Cu(NH 3 ) 4 SO 4 +NH 4 OH+10KCN = 

Colorless 

2K s Cu(CN) 4 +2K 2 S0 4 +NH 4 CN+NH 4 CN0+7NH 3 . 

H 2 S does not precipitate CuS when passed into a solution containing 
K 3 Cu(CN) 4 . 


CADMIUM 

27. To a solution of cadmium chloride add 1 cc. HC1, dilute 
to 10 cc., pass in H 2 S; note the color of the precipitate CdS. 

Reaction.—CdS0 4 +H 2 S = CdS+H 2 SO 4 . 

28. Test the solubility of CdS in (NH^S* solution. 

29. Follow out directions as given in the copper tests. Note 
color of Cd 2 Fe(CN) 6 - 

30. Does KCN prevent the precipitation of CdS? 

Reaction.—K 2 Cd(CN) 4 is formed by the action of KCN on the cadmium 
salt. When H 2 S is passed into this solution the reaction takes place as 
follows: 

K 2 Cd (CN) 4 +H 2 S=CdS+2KCN+2HCN. 




60 


QUALITATIVE ANALYSIS 


Outline of the Procedure for Separation of Members of the 
Hydrogen Sulphide Group. 

For convenience the members of the hydrogen sulphide 
group have been classed under two subdivisions, owing to the 
fact that the sulphides of some are soluble in ammonium poly¬ 
sulphide, while the others are scarcely affected by this reagent. , 
Antimony, arsenic and tin sulphides dissolve, while the sulphides 
of bismuth, cadmium, copper, lead and mercury are practically 
insoluble. • The separation of these subgroups is accomplished 
by dissolving the soluble sulphides in (NH^S* solution, filter¬ 
ing, and washing the residue. 

The chemical reactions of the insoluble subgroup have 
shown certain characteristics of the members which enables j 
us to separate the four elements from one another. The fact I 
that the sulphide of mercury is not dissolved by dilute nitric 
acid makes it possible to isolate HgS from the other sulphides, I 
which dissolve. The fact that lead sulphate is practically insoluble j 
in dilute sulphuric acid gives a procedure for removing lead from 
bismuth, cadmium and copper, since the sulphates of these 
elements dissolve in dilute sulphuric acid. Bismuth hydroxide 
precipitates when ammonia is added to a solution of bismuth; ‘ 
copper and cadmium, on the other hand, form soluble com¬ 
pounds and may be removed by filtration. Copper is recognized 
in the filtrate, if present in appreciable amount, by the blue 
color the ammonium compound imparts to the solution. The 
sulphide of cadmium may be precipitated from its solution in 
presence of KCN; the sulphide of copper does not precipitate, ' 
hence separation may be made. The isolated substances may 
now be confirmed by special tests. 



THE METALS 


61 


Separation of the Hydrogen Sulphide Group 


Heat the filtrate of the HC1 group, or an acid solution containing the 
embers of the H 2 S group (1 part HC1 (1.12) to 10 parts of the solution) in an 
rlenmeyer flask, nearly to boiling. Pass in H 2 S to saturation (5-10 min.) 
3 eping the solution hot. Now add one and a half volumes of water and 
rain saturate with hydrogen sulphide. Cork the flask, shake, and allow ppt. 
> settle. Filter, and wash the precipitate with hot water. 


Precipitate.—Black—HgS, PbS, CuS. 
Brown—Bi 2 S3, SnS. 

Orange—Sb 2 S 3 , Sb 2 S 5 . 

Yellow—CdS, As 2 S 3 , As 2 S 6 , SnS 2 . 
(PtS 2 , Au, Au 2 Si- 3 , Se, Te, Mo, etc.) 


Filtrate.—Ions of the following 
groups together with acid anions. 
Expel H 2 S by boiling and save for 
the analysis of these groups. 


Separation of the Soluble and Insoluble H 2 S Sub-groups, A and B 

Transfer the precipitate to a small dish. Add 5-10 cc. (NH4) 2 S X . (Omit 
le addition of (NH 4 )S X if the analysis does not include the Soluble H 2 S Sub- 
roup.) Warm the mixture (40°-50°) 10 min. Add 10 cc. H 2 0, filter, and 
ash with hot water. (Add to the wash water 5 per cent of solid NH 4 N0 3 
the precipitate passes through the filter paper.) Hg being absent, NaOH 
lay be used in place of (NH 4 ) 2 S X . 


II. 


Residue Subgroup, A.—HgS, PbS, CuS, 
)dS, Bi 2 S 3 . (PtS 2 ; Au and Au 2 Si_ 3 ; 
nSi_ 2 ; BaS0 4 .) To the residue in a cas- 
srole add 5-10 c.c. HN0 3 (sp.gr. 1.20) to 2 
ols. H 2 0. Heat to boiling and boil for 
sveral minutes. Filter and wash the 
recipitate. (Prolonged boiling is apt to 
Dim insoluble PbS0 4 , hence should be 
voided.) 


Filtrate Subgroup, B.— 

(NH 4 ) 3 AsS 4 . 

(NH 4 ) 3 SbS 4 , (NH 4 ) 2 SnS 3 , and 
possibly(NH 4 ) 2 PtS 3 , (NH 4 ) 3 AuS 3 , 
together with rare elements. Save 
for the analysis of the Soluble H 2 S 
Subgroup. 
















QUALITATIVE ANALYSIS 


62 


Separation of Members of the Insoluble H 2 S Subgroup A 

IV. 


Residue.—HgS or Hg(N0 3 ) 2 HgS, white. 
(Sn, Au, Pt may be present.) Tear off the 
portion of the filter containing residue, put 
into a casserole, and add 25 cc. of bromine 
water. Warm the covered casserole; stir 
frequently (5-10 min.); boil to expel Br, 
and filter. 1 (KC10 3 added hastens solu¬ 
tion.) To the filtrate add, drop by drop, 
SnCl 2 solution. A white precipitate turning 
gray, with an excess of SnCl 2 , indicates 
Mercury, as HgCl or Hg. 

Filtrate. — Pb" 1 " 4- , Bi+ + ‘ 
Cu + + , Cd++, N0 3 “. (Bariu: 
may be present). Add 4 c 

H 2 S0 4 (cone.) and evaporate in 
casserole until white fumes a] 
pear. Cool and pour into 10 c 
of cold water, rinsing out the dis! 1 
Shake, and allow to settle 4 mi; 
Filter and wash the precipita 
with dilute H 2 S0 4 (1.20), arJ 
finally with water. 

V. 




Precipitate.—PbS0 4 , white (BaS0 4 and (Bi0) 2 S0 4 
may be present.) Dissolve by adding 10 per cent sol. 
NH 4 C 2 H 3 0 2 and pouring steadily through filter. To 
the filtrate add 3 cc. 30 per cent sol. HC 2 H 3 0 2 and a 
few drops of K 2 Cr0 4 . A yellow precipitate proves 
the presence of lead. 

Filtrate. — Bi+ + ^ 
Cu++,Cd + +,S0 4 — 
Add NH 4 OH unt 
strong odor of ammoni 
persists, on shakinj 
Filter and wash th 

copper and cadmium compounds. 

VI. 



precipitate to remov 

Precipitate.—Bi(OH) 3 , white. Dissolve by pour¬ 
ing a few cc. HC1 on filter. Evaporate filtrate almost 
to dryness. Add 2 cc. H 2 0 and pour this into beaker 
containing 100 cc. warm water. A white ppt. is 
BiOCl. Filter, wash once, and add on filter a few cc. 
Na 2 Sn0 2 . A black stain is bismuth. 

Filtrate.— 

Cu(NH 3 ),+ + blui 

Cd(NH 3 ), ++ , SO,- 

Divide into two poi 
tions, a and b. 




(a) Acidify small portion with acetic 
acid, add 2-3 drops of K 4 Fe(CN) 6 , pour 
on filter; a pink color is due to 
Cu 2 Fe(CN) 6 , proving the presence of 
copper. (Cd 2 Fe(CN) 6 is white.) 

(b) Add solid KCN to destro 
color. Pass in H 2 S. A yellow ppt. i 
CdS, proving the presence of cad 
mium. 

If the precipitate is dark it may b 

due to Bi or Pb contamination. 

----- 1 


1 If an insoluble precipitate remains, it is probably Sn0 2 or Sb 2 0 3 . Fus 
with Na 2 C0 3 +S and treat sulphides according to procedure in Soluble H 2 1 
Subgroup. 
























THE METALS 


63 


Optional Method for Precipitation of the H 2 S Group and the Separation 
of its Divisions 

Precipitation.—To a given quantity of the solution add one-ninth of its 
tume of concentrated HC1 and a few drops of HN0 3 . If much acid is 
eady present allowance must be made for it. Transfer the mixture to an 
lenmeyer flask and boil to half vol. under the hood. Pass a rapid stream 
H 2 S through the hot liquid, heating again to boiling once or twice and 
iking vigorously. When no more precipitate forms (5 to 10 minutes), 
d enough water to make the volume a little more than twice the original, 
mtinue to pass the gas into the solution until the liquid is cold and no more 
ecipitate falls (10 to 15 minutes), filter, and wash. 

Separation of the Divisions.—Transfer the precipitate to a beaker, cover it 
th concentrated ammonium hydroxide, pass in a rapid stream of H 2 S for 
to or three minutes, warm gently, shake well, filter, and wash. The sul¬ 
fides of arsenic, antimony, and tin dissolve promptly, leaving mercury, 
pper, lead, bismuth, and cadmium as a precipitate of sulphides. The 
trate and residue are now treated in the usual way. 

otes on the Insoluble H 2 S Subgroup A and the Precipitation of the 

General Group 

I. If HN0 3 has been used in dissolving the original substance, and is 
resent to any extent, it should be removed by evaporation with HC1; other- 
ise, will be oxidized to H z O and free S. The presence of other oxidizing 
ibstances may also liberate free S. 2FeCl 3 +H 2 S = 2FeCl 2 +2HCl+S. 

Arsenic precipitates best in hot solutions of HC1(1.12) 1 :10. Further- 
Lore, the oxyhlorides of bismuth and antimony do not form. 

Arsenic precipitation takes place slowly; haste will cause loss and subse- 
aent errors. 

Lead, cadmium, and tin are best precipitated in dilute, cold solutions. 

Acidity Test. — The sulphides of this group are precipitated in presence 
■ f re e hydrochloric acid. If the acidity is insufficient precipitation of zinc 
lay occur along with the H 2 S group. On the other hand HC1 present in 
rger amount than recommended in the procedure will prevent complete 
recipitation of members of the H 2 S group. The following acidity test 
ill be found useful. 

A drop of .solution placed on an indelible lead pencil mark gives a blue 
jot for less than 2 per cent HC1 (1.20); pea green = approx. 5 per cent; 
ellow=over 10 per cent. 




64 


QUALITATIVE ANALYSIS 


Color Indications.—Hot solution: White or yellowish turning to black, di 
to HgCl22HgS —>HgS. Orange is due to Sb 2 S 3 and CdS. Yellow is Asj 
or SnS 2 . All other sulphides of the H 2 S group are black. 

II. When cone. HNO,i has been used to dissolve the substance, t 
reagent (NH 4 ) 2 S is better than (NH 4 ) 2 S X for dissolving the SnS 2 and Sb; 
formed, due to the higher valence produced by oxidation, but SnS and Sb 2 
do not readily dissolve in the monosulphide, and the polysulphide must 
used when the elements Sn and Sb have the lower valence. CuS and H 
dissolve to a slight extent in the latter. 

Gold and platinum may be found either with the soluble or insolul 
subgroups or in both, though they generally pass into the soluble subgrov 
and are tested for there. (Molybdenum colors the solution of (NH 4 ) 2 S X oranj 
red. The soluble subgroup may contain the rare elements selenium and t 
lurium.) The filtrate under II should be boiled free of H 2 S immediate 
on collecting, if later groups are to be looked for in this solution. 

If the acid has not been removed from the precipitate this will decompc 
(NH 4 ) 2 S x with the separation of sulphur. A light-colored residue therefc 
does not indicate the presence of the insoluble H 2 S Subgroup A. 

III. The sulphides PbS, Bi 2 S 3 , CuS and CdS dissolve readily in HN0 3 
the strength indicated in the analysis. Long boiling will act on the HgS. 

A black residue is not to be taken as proof for the presence of mercui 
as it may be sulphur inclosing mechanically small quantities of black sulphide 
Hence this residue should be tested for mercury as directed. 

Note .—Prolonged boiling of the residue III may form PbSO« and ba: 
mercuric sulphate, hence must be avoided. 

IV. Bromine water dissolves the sulphides of mercury, platinum, ai 
gold. Tin remains in the residue if undissolved by the polysulphide. T1 
addition of the solid, KC10 3 , hastens solution, but also dissolves tin. 

Platinum and gold are reduced by SnCl 2 , coloring the solutions reddi; 
brown and purple respectively. Platinum precipitates in a saturated soluti< 
of KC1. Gold forms a purplish black or dark yellow precipitate in the presen 
of Na 2 Cr0 4 +H 2 C 2 0 4 solution. 

The purpose of boiling the solution until the white fumes of H 2 S0 4 appe 
is to expel HN0 3 , in which PbS0 4 is soluble. A residue remaining aft 
treatment of the HgS precipitate with the solvents indicated may be Sn( 
or Sb 2 0 3 . Fuse with Na 2 C0 3 -j-S and treat sulphides as members of tl 
Soluble H 2 S Group. 

V. Dilute H 2 S0 4 decreases the solubility of PbS0 4 . Bismuth ar 
barium may be present, but lead can be separated by means of its solubilii 
as a sulphate in ammonium acetate (BaS0 4 insoluble) and the insolubilii 
of the chromate salt in acetic acid, whereas the chromate of bismuth is solubl 




THE METALS 


65 


;ain, lead chromate is soluble in KOH, whereas the bismuth salt is in- 
luble. 

VI. A dark color in (6) VI may be due to a trace of lead or bismuth, 

, possibly, to copper. KCN removes color due to copper. The addition 

NH4OH will precipitate Fe(OH) 3 , etc., if that group is not completely 
moved in the washing. 

Cd(OH) 2 + or Cu(OH) 2 + first formed are dissolved in the excess of 
H 4 OH, forming Cd(NH 3 ) 4 + + and Cu(NH 3 ) 4 + + ; the latter is blue. 

Bi(OH) 3 , white, is precipitated by NH 4 OH, due to hydrolysis. BiOCl is 
;s soluble in water at higher temperatures, hence it is better to add the 
lC 1 3 to warm water. 

The presence of an excess of acid will prevent precipitation of bismuth 
le to the reversible reaction BiCl 3 -fH 2 0 BiOCl+2HC1. The large 
;cess of acid may be neutralized by NH 4 OH added drop by drop, taking 
xe to keep the solution slightly acid. 

Sodium stannite, Na 2 Sn0 2 , should be prepared as needed, e.g. 10 per cent 
aOH is added to 10 per cent SnCl 2 until the precipitate Sn(OH) 2 first formed 
£t dissolves. This reagent reduces BiOCl to black metallic Bi, and is a 
?ry delicate test; small quantities may thus be detected. 

The confirmatory test for bismuth should be made, as lead may appear 
me and be mistaken for bismuth. 

In case Cu 2 Fe(CN) 6 is present only in small amounts, it can best be seen 
y pouring the solution through a filter paper, which will be stained pink 
Y the precipitate. Cd 2 Fe(CN) 6 being white does not interfere with the test. 

KCN forms Cu 2 (CN) 2 and Cd(CN) 2 ; the former is stable. KCN first 
irms a yellow precipitate Cu(CN) 2 decomposing into white cuprous cyanide, 
uCN+cyanogen with an excess of the reagent the precipitate dissolves, 
uCN+3KCN = K 3 Cu(CN) 4, colorless solution. H 2 S precipitates CdS, 
sllow, but not CuS, a fact taken advantage of in the separation of copper 
om cadmium. A black precipitate will be obtained should lead or mercury 
e present, as is occasionally the case. Mercury will find its way into this 
)lution if the original H 2 S precipitate has not been washed free of HC1, 
nee this would yield aqua regia upon addition of HN0 3 and dissolve 
)me of the mercury. Lead may be present due to incomplete removal, 
if a black precipitate is obtained, filter and treat the residue with dilute 
[ 2 S0 4 . PbS0 4 will remain on the filter and CdS0 4 pass into solution. The 
ltrate may now be tested for cadimum by again passing in H 2 S. 

Optional Method.— Professor Hinds gives the following advantages for 
lis method of procedure. (1) A definite acid concentration is obtained, 
ipon concentration a twice normal solution of HC1 results, from which arsenic 
3 adily precipitates. Dilution to twice the original volume gives a half 






66 


QUALITATIVE ANALYSIS 


Stopcock 



Fig. 12.— Scott’s Hydrogen Sulphide Generator. 

Fig. 12 shows a convenient form of a generator for obtaining hydrogen sulphide i 
HP, P ressure - . The cylinder A A is constricted, as shown, to support perforated h 
disk G, upon which rests the iron sulphide. The lower end of the chamber is closed to cai 
small particles of FeS that may be carried through the perforations of the disk. Sir 
openings admit the acid to A . The level of the acid is below the disk G, so that the a 
u 1 il con tact with su ^Phide when pressure is applied by means of the rubl 

bulb E, the stopcock & being open and <S 3 closed. The mercury gauge C is adjusted to bl 
out at a gn en pressure, to prevent accident, the bulb D preventing the mercury from be 
blown out of the apparatus. A small opening in D allows the escape of the gas. When i 
apparatus is in operation, H is connected to an empty heavy-walled bottle, which in ti 
is attached with glass tube connection to the pressure flask in which the precipitation 
the sulphide is made, the flask being closed to the outside air. By pressure on the rubl 
bulb E, acid is forced into the chamber A' past the disk into the sulphide in A The ent 
system will now be under the pressure indicated by the gauge C. The pressure is releas 
by opening the stopcock S 2 and the flask containing the precipitate then disconnect 
The reservoir is designed to hold about two liters of acid, and the cylinder contain! 
the sulphide is of sufficient capacity to hold over one pound of FeS, so that the apparal 
will deliver a large quantity of hydrogen sulphide. 


































































THE METALS 


67 


mal HC1 solution, necessary for the complete precipitation of other mem- 
s of the Group. (2) Oxidation with HN0 3 is to insure tin being present 
the higher valence so that it may be precipitated as stannic sulphide, 
which form it is more readily soluble in colorless ammonium sulphide. 
The use of yellow ammonium sulphide is avoided. Copper sulphide 
Dnly slightly soluble in colorless ammonium sulphide. (4) The time is 
ch shortened, 30 to 45 minutes being sufficient for the whole process. 

The concentration of the solution must be above 0.125 N-HC1, to prevent 
precipitation of the metals of succeeding groups. 


68 


QUALITATIVE ANALYSIS 


Chemical Reactions 

Soluble H 2 S Subgroup, B (Tin Group) 

ARSENIC—As + ++ , As + + + + + 

Since there are two series of salts of arsenic, the prelimina 
tests should be made with both forms. For arsenous acid u 
AS 2 O 3 dissolved in HC1. For arsenic acid use H 3 ASO 4 . Coi 
parative tests of the two forms may be made on samples side 1 
side. 

1 . Add 10 cc. of water and 2 cc. HC1 (1.20). Pass in H 
gas and note the fact that the sulphide (AS 2 S 3 ) from arseno 
acid precipitates more readily than from arsenic acid. H 2 S fii 
reduces the arsenic acid with separation of sulphur and th 
precipitates AS 2 S 3 . By heating the solution, the precipitation 
the latter is hastened. 

Reactions.— (a) H 3 As 0 4 -|-H 2 S= : | S-I-II 2 O-I-H 3 ASO 3 . 

(6) 2H 3 As0 3 +3H 2 S= I As 2 S 3 +6H 2 0. 

Note .—From strong HC1 solutions and by rapid passage of H 2 S, As 2 S, 
precipitated. Try this: 

Reaction—2H 3 AsO 4 +5H 2 S= 1 As 2 S 5 +8H 2 0. 

2 . Test the solubility of a portion of each sulphide by pouri: 
repeatedly over the separate precipitates 5-10 cc. (NH 4 ) 2 S X . 

Reactions.—(a) As 2 S 5 +3 (NH 4 ) 2 S = 2 (NH 4 ) 3 AsS 4 . 

(b) As 2 S 3 +3(NH 4 ) 2 S x =2(NH 4 ) 3 AsS 4 +S x . 

3. Unite the two filtrates. Acidify with HC1 (1.12), and no 
the re-precipitation of the sulphides. Filter and wash the pi 
cipitate. 

Reaction.—2(NH 4 ) 3 AsS 4 +6HC1= f As 2 S 6 + T 3H 2 S+6NH 4 Ci. 

4. In a porcelain dish (casserole is best) test the solubility 
a portion of the As 2 S 5 by warming with 5 cc. HC 1 ( 1 . 20 ). Nc 



THE METALS 


69 


add a few crystals of KCIO3, a crystal at a time, until complete 
solution takes place. Filter. Sulphur will remain on the filter. 

Reactions.—(a) 2HC1+KC10 3 =KC1+H 2 0+C10 2 +CL 

(6) As 2 S 3 +8H 2 0+10C1= |3S+10HC1+2H 3 AsO 4 . 

5. Divide the solution in two portions. Test one portion by 
the Gutzeit test. 

Reaction.—2H 3 As0 4 +8H 2 (from Zn+2HC1) = 2AsH 3 +8H 2 0. 

6 . Make the other portion alkaline with NH 4 OH, adding a few 
drops in excess, then add magnesia mixture, and stir with a glass 
rod. A white crystalline precipitate forms slowly, MgNH 4 As0 4 . 

Reaction.—H 3 As0 4 +MgCl 2 +NH 4 Cl = | NH 4 MgAs0 4 +3HCl. 

The reaction takes place with arsenic (As +++++ ) and not 
with arsenous (As +++ ) salts or acids. This may serve as a 
distinction between the two forms. 

7 . Siver nitrate test.—AgNC >3 solution added to a neutral 
solution of an arsenite precipitates Ag 3 As 03 yellow or chocolate 
brown. No precipitate forms with arsenates. 

H 3 As0 3 +3AgN0 3 = | Ag 3 As0 3 +3HN0 3 . 

8 . If the arsenic is in a nitric acid solution, heat gently until the 
brown fumes are expelled, dilute with 5 cc. H 2 O, filter, add 5 cc. 
of AgNC >3 solution (if cloudy, filter) to the clear solution, add a 
drop of phenolphthalein, make first alkaline with NH 4 0H and 
then faintly acid with 5 per cent acetic acid solution; a chocolate 
colored precipitate is Ag 3 As 03 . 

ANTIMONY 

9 . Use solutions of SbCl 3 and SbCl 5 in presence of HC1. Try 
the reactions separately on the two solutions. Warm and pass 
in H 2 S. Note the color of the precipitates in each case. 

Reactions.—(a) 2SbCl 3 +3H 2 S — i Sb 2 S 3 -1- 6HC1. 

(6) 2SbCl5+5H 2 S= I Sb 2 S 6 +10HC1. 


70 


QUALITATIVE ANALYSIS 


10. Dissolve in yellow ammonium sulphide, as in the case 
of arsenic. Re-precipitate by acidifying the filtrate with HC1. 

Reactions.—(a) Sb 2 S 3 +3(NH 4 ) 2 S x = 2(NH 4 ) 3 SbS 4 +S x . 

(6) 2(NH 4 ) 3 SbS 4 +6HCl = i Sb 2 S 5 + T 3H 2 S+6NH 4 C1. 

(c) Sb 2 S 3 +3(NH 4 ) 2 S=2(NH 4 ) 3 SbS 3 . 

(d) 2(NH 4 ) 3 SbS 3 +6HCl = Sb 2 S 3 + T3H 2 S+6NH 4 C1. 

(e) Sb 2 S 6 +(NH 4 ) 2 S = 2(NH 4 ) 3 SbS 4 . 

11. Dilute with an equal volume of water, filter, and boil the 
precipitate with HC1 (1.20); tho sulphide dissolves. 

Reactions.—(a) Sb 2 S 3 +6HCl = 2SbCl 3 + T 3H 2 S. 

(6) Sb 2 S 5 +6HCl = 2SbCl 3 -U2S+T3H 2 S. 

Observe that in either case SbCl 3 is formed. 

12. Divide in two portions. Boil to remove some of the acid. 
Pour one portion over a large piece of zinc in contact with platinum 
foil. (Hood if As is present.) The antimony will be reduced 
and form a black deposit on the platinum. 

See Introduction for the Electromotive Series, page 14. 

13. Wash the foil carefully, and place in a solution of hypo¬ 
chlorite. The stain is insoluble; arsenic will dissolve. See 
Marsh test for Arsenic, page 53. 

14. If the stain is dissolved in fuming nitric acid, tartaric acid 
added, the solution warmed to expel the brown fumes, then 
diluted to three volumes with water and a few drops of HC1 added, 
hydrogen sulphide will precipitate orange Sb 2 S 5 . 

15. Dilute the other portion to four volumes and pass in H 2 S; 
an orange precipitate will be thrown out. Write out the reactions. 

16. Dilution of SbCE or SbCl.5 solutions with water, if in¬ 
sufficient HC1 is present, will cause precipitation of the oxychlo¬ 
rides, SbOCl or Sb0 2 Cl. 

Reactions.—SbCl 3 -f H 2 0 <=» J. SbOCl+2HC1. 

SbCl 6 +2H 2 0^± | Sb0 2 Cl+4HCl. 

17. The precipitates are soluble in tartaric acid, distinguishing 




THE METALS 


71 


antimony from bismuth, BiOCl being insoluble. Prove these 
statements by qualitative tests. 

TIN 


Use solutions of SnCl 2 and SnCl 4 in presence of HC1. Try 
the reactions separately on the two solutions, noting any difference 
in results. 

18. Warm the solution and pass in H 2 S gas. Note the color 
of the precipitates. 

Reactions. — (a) SnCl 2 +H 2 S = [ SnS+2HCl. 

(6) SnCl 4 +2H 2 S = 1 SnS 2 +4HCl. 

No te. _SnS and SnS 2 are readily soluble in HC1 (1:1). The solutions 

used should contain not over 2.5 per cent concentrated HC1. 


19. Test the solubility of the sulphides in yellow ammonium 
sulphide and in colorless ammonium sulphide. In the latter 
SnS 2 is soluble, SnS insoluble, hence, the necessity of using 
(NH 4 ) 2 S x in separating this group from the insoluble group. 


Reactions 


__( 0 ) SnS + (NH 4 ) 2 S X = (NH 4 ) 2 SnS 3 +S x . 
(5) SnS 2 +(NH 4 ) 2 Sx = (NH 4 ) 2 SnS 3 +Sx* 
(c) SnS 2 +(NH 4 ) 2 S = (NH 4 ) 2 SnS 3 . 


20. Add HC1 to the solutions obtained; the sulphide of tin 
SnS 2 is precipitated. 

(NH 4 ) 2 SnS 3 +2HC1 = i SnS 2 + T H 2 S+2NH 4 C1. 


21. Stannic Chloride and Stannous Chloride—To a solution of 
SnCk add HgCl 2 . Observe that no precipitate forms. Now 
try the same test with a solution of SnCl 2 ; the precipitate is 
HgCl or HgCl+Hg or Hg alone, depending upon the amount 

of reagent used. . , ...» 

22. To a fresh portion add some pieces of zinc, and acidify 

with HC1. Stannic tin will be reduced and deposit on the zinc. 
See Electromotive Series in Introduction. 






72 


QUALITATIVE ANALYSIS 


23. Scrape off the spongy tin and dissolve in HC1. Now add 
HgCl 2 ; a white or gray precipitate will form. What inference 
do you draw as to the valence of tin obtained in solution in this 
way? 

Write out reactions. 

24. When zinc is placed over platinum and the tin solution 
poured over it, no stain will be deposited on the platinum, but a 
spongy deposit will cover the zinc or separate in the solution. 

25. Observe in the second solution that H 2 S does not cause a 
precipitate of SnS when the liquid is strongly acid, but when 
diluted the sulphide will readily precipitate. Advantage is 
taken of the fact that Sb will precipitate in an acid solution of a 
definite strength, as stated above, while Sn will remain in solution. 
See first method of analysis. 

Metastannic acid.—When hot dilute HN0 3 acts on metallic 
tin, a white substance is obtained known as metastannic acid, 
Sn 50 s(OH)io or 5 (H 2 Sn 03 ). This is a polymer of stannic 
hydroxide, H 2 Sn0 3 . The compound is insoluble in acids. The 
compound boiled with concentrated HC1 forms Sn 5 0 5 Cl2(0H) 8 , 
insoluble in HC1, but soluble in water. 

26. With a solution of Sn 5 05 Cl 2 ( 0 H )8 make the following tests: 

a. To a portion add HC1. The ppt. = Sn 5 05 Cl 4 ( 0 H) 6 - 4 H 2 0 . 

b. To a second portion add NH 4 OH. The ppt. is 5(H 2 Sn0 3 ). 

c. Pass in H 2 S into a third portion. The ppt. = SnS 2 . 

Stannic compounds are converted into metastannic forms by 
diluting and boiling. Metastannic compounds are converted 
into stannic form by boiling with strong KOH or HC1. Stannic 
compounds dissolve in acids. Metastannic compounds are 
insoluble in acid. 




THE METALS 


73 


Gold, Platinum and the Less Common Elements of the Hydrogen 
Sulphide Group 

The properties and characteristic tests of the less common elements 
of the Hydrogen Sulphide group are given in Part VI. 

Tables of Reactions 

The student is referred to the tables given in Part V for a comparative 
study of characteristic reactions of the members of the group. The list of 
reagents used for the tests is given in the first column on the left, the salts 
of the group elements are indicated at the top of the pages and the product 
formed is shown at the intersection of the columns of the reagent and the 
element in question. The reaction tables will be found useful for reference 
and may be used for additional tests for laboratory practice. 


74 


QUALITATIVE ANALYSIS 


Outline of Procedure for Separation of Antimony, 
Arsenic and Tin 

The sulphides of antimony, arsenic and tin dissolve in yellow 
ammonium sulphide, permitting these compounds to be separated 
from bismuth, cadmium, copper, lead and mercury. If the 
solution is acidified the sulphides re-precipitate. Arsenic sulphide 
may be isolated by treating the combined sulphides with strong 
HC1, since this compound does not dissolve, whereas the sulphide 
of antimony and tin pass into solution as chlorides. 

Two methods are given for separation of antimony and tin. 
The first takes advantage of the varying solubility of antimony 
sulphide and tin sulphide in hydrochloric acid of definite strength. 
The second procedure utilizes the principle outlined under Electro¬ 
motive Series in the Introduction. Metallic iron for example 
displaces antimony from its combination as a salt, metallic 
antimony being liberated; tin on the other hand is simply reduced 
from stannic to stannous condition and remains in solution. 
Confirmatory tests may now be made for arsenic, antimony and 
tin on the isolated portions. The directions follow: 


Separation of the Soluble H 2 S Subgroup—B (Tin Group) 
Procedure A 

I. Dilute the yellow ammonium sulphide solution (filtrate of the Insoluble 
H 2 S Subgroup containing (NH 4 ),AsS 4 , (NH 4 ) 3 SbS 4 , (NH 4 ) 2 SnS, and the 
excess (NH 4 ) 2 S X ), with about 25 cc. H 2 0. Add HC1 (sp. gr. 1.12) until dis¬ 
tinctly acid (not over 2.5 per cent strong HC1), warm for a few minutes on a 
water bath, shaking frequently Filter, wash by suction, and drain the water. 1 

1 For preliminary practice use solutions of AsCl, SbCl 3 and SnCl 4 con¬ 
taining 2.5 per cent free cone. HC1, and precipitate the sulphides by saturat¬ 
ing with H 2 S. 




THE METALS 


75 


II. 


Precipitate. —As 2 S 3 , As 2 S 6 , yellow; Sb 2 S 3 , Sb 2 S 5 , orange; 
SnS, brown, SnS 2 , yellow. (PtS 2 , Au a Si_ 3 , Se, Te, Mo.) Trans- 

Filtrate.— 

Reject. 


fer to a small beaker, add 10 cc. HC1 (sp. gr. 1.2), and digest 

for 10 minutes, placing beaker in boiling water; stir frequently, add 5 cc. H a O, 

filter, and wash once with 5 cc. of water. 

Ill 


Precipitate . —As J3 5 (PtS 2 , Au, etc.). Wash with HC1 (sp.gr. 1.12) 
once, and finally with hot water. Warm the residue with about 
10 cc. HC1 (sp.gr. 1.12); add KClOs a crystal at a time,until the 
precipitate dissolves. Skim off the sulphur with a spatula. (If 
Pt and Au are to be tested, evaporate the solution to small bulk 
(2-3 cc.). A yellow precipitate indicates Pt. Filter and test 

■---the residue for Pt as below). The solu- 

Precipitate. — tion contains H 3 As 04 (AuC 1 3 , etc.). 

K 2 PtCl 6 , yellow. Make solution alkaline with NH 4 OH; 

Dissolve in 2 cc. hot (Filter if ppt. forms = Hg) add several 
water add a few drops of magnesia mixture, rub sides of 
drops of KI solu- test tube with glass rod. A crystalline, 
tion; a deep red is whitish precipitate forming slowly, espe- 
due to K 2 PtL. daily where the rod has touched the sides 

_-of the tube, proves the presence of 

Arsenic. (If gold is to be tested for, it will pass into the 
filtrate together with the rare elements of the group, Se, Te, 
and Mo.) The method of detection is given below. Arsenic 
may be tested by the Gutzeit or Marsh test in place of 
the method above given, when the detection of gold is not 
desired. 

Filtrate.— 

Sb+ + + Cl s “, 

Sn ++++ Cl4- 

Dilute to 

50 cc. with 

water; heat 

to about 90°; 

saturate with 

H 2 S (5 min.), 

keeping solu¬ 
tion hot; add 

5 cc. water 

Solution contains AuC 1 3 , etc. Add 5 cc. of a saturated 
solution of oxalic acid; evaporate to about 3 cc.; make acid if 
necessary with more H 2 C 2 04 , and add 10 cc. Ii 2 0. Digest on 
water bath several minutes—purple or dark yellow is due to 
Au. (Rarer elements will be in the filtrate if solution is 
filtered.) 

and again 

pass in H 2 S. 

Filter while 

hot. 

















76 


QUALITATIVE ANALYSIS 


IV. 


Precipitate. Sb 2 S 3 , 
orange red. 

Confirm. Dissolve 
in a few drops of HC1 
(sp gr. 1 12). Pour the 
solution over a platinum 
foil on which is placed a 
piece of tin. After sev¬ 
eral minutes add a little 
water and remove Pt 
foil and wash carefully. 
A black stain, insoluble 
in NaCIO, proves Anti¬ 
mony. 


Filtrate. Sn + + + + Cl 4 - . To insure removal of 
Sb, add 5 cc. H 2 0, then pass in H 2 S to hot solution; i 
filter if precipitate forms. Allow the solution to cool, j 
and then pass in H 2 S for 5-10 minutes. If a yel¬ 
lowish or brownish precipitate begins to form, tin is 
indicated. 

Confirm. Evaporate to 5-10 cc.; pour over a 
piece of zinc (C.P. about 1 g.). Tin will precipitate 
in a spongy form over the zinc. Wash by decanta¬ 
tion. Remove the Zn. Scrape off and dissolve spongy 
Sn in 2-5 cc. hot HC1 (1.20) (Pt hastens action.) ■ 
Add 1-2 cc. water and filter, allowing filtrate to drop 
into 2-3 cc. HgCl 2 solution. A white or gray ppt. 
proves Tin. 




















;i 


THE METALS 


77 


Optional Method of the Analysis of the Soluble H 2 S Subgroup 

The processes I and II of precipitating arsenic antimony and tin as sulphides 
id separating arsenic from antimony and tin by means of HC1 (sp. gr. 1.20) 

e the same as in the first met hod, sections I and II. __ 

Filtrate.—Sb+ *+Cl 3 “, Sn+ + + + Cl4~. Heat 

to boiling to remove hydrogen sulphide, allow to 
cool, and divide in two portions. 

1. Pour the solution in a test tube and insert 
two iron nails. Heat, adding more HC1 if 
necessary to generate hydrogen. Antimony is 
precipitated on the nails and may be tested as 
described in (a). SnCl 4 is reduced to SnCl 2 . 
Filter quickly into 1 cc. of a solution of HgCl 2 ; a 
white or gray precipitate resulting shows tin to 
be present. 

2. Pour the second portion into a small 
evaporating dish containing a platinum foil in 
contact with a piece of zinc or tin. Antimony 
will deposit as a black stain on the platinum 
and may be confirmed according to (a). Tin 
will precipitate in spongy form and may be 
treated according to (6). 


Precipitate.—As 2 S 5 
ransfer to a test tube; add 
-4 cc. of strong HN0 3 ; 
}il until the precipitate dis- 
jlves: test (A) make slight- 
alkaline with NH 4 OH, 
id add three grams of solid 
H4CI and a piece of mag- 
esium ribbon. Insert a 
»ose cotton plug; cover the 
louth with a piece of filter 
aper moistened withHgCL- 
n 10 to 15 minutes a brown 
r black stain will appear 
n the paper if Arsenic is 
resent. 

Test (B) Follow direc- 
ions in 7—under reactions 
or Arsenic. 


(a) The stain of metallic antimony 
3 insoluble in NaOCl and in NaOBr. 
f the stain is dissolved in fuming nitric 
tcid, and the nitric removed by warni¬ 
ng in the presence of a little tartaric 
icid until brown fumes cease, a few 
Irops of HC1 added, the solution di- 


(5) The metallic tin may be brought 
into solution by boiling with strong 
HC1 in presence with a platinum foil. 
The filtrate may now be tested with 
HgCl 2 solution. The precipitate 
indicates reduction by tin. NH4OH 
will blacken the precipitate. 


uted and H 2 S passed in, an orange 
lolored precipitate will prove Sb 2 S 6 . 


















78 


QUALITATIVE ANALYSIS 



Notes on the Soluble H 2 S Subgroup, B 


I. If a finely divided white or light yellow precipitate forms on th 
addition of HC1 to the filtrate of the insoluble H 2 S subgroup, the precipitat 
is largely sulphur, and the presence of the soluble group is doubtful. A prc 
nounced yellow color indicates arsenic or tin; an orange color indicate 
antimony. If CuS or HgS is present, the precipitate will be dark. 

The acidity should not exceed 2:5 cc. strong HC1 per 100 cc. of solutior 
otherwise tin will not be completely precipitated. 

II. Since Sb 2 S 5 dissolves but slowly, digestion with HC1 (sp.gr. 1. 2) must fc 
continued several minutes to insure its solution. Boiling is avoided to prc 
vent the volatilization of HC1, thus weakening the solution and to avoi i 
dissolving arsenic sulphide, which may occur by direct boiling. In cas 
As 2 S 3 dissolves, it will appear in the Sb test. The stain of arsenic, howevei 
is soluble in a hypochlorite, whereas antimony is not. 

The separation of arsenic from antimony may also be accomplished a 
follows: 

Add a few crystals of FeS0 4 to the solution containing the arsenic an 
antimony compounds. Construct a generator, as described in the Mars 
test, with a delivery tube passing into a beaker, containing a solution of silve 
nitrate, in place of the hard glass tube. When the hydrogen begins to b 
freely evolved, add the solution to be tested. Stibine and arsine enterin 
the silver solution will immediately produce a precipitate of metallic silve 
and silver antimonide, arsenic remaining in solution. The silver that sti 
remains in the ionic form may be removed from the solution by precipitatin 
it out as a chloride by the addition of HC1 (1.12), drop by drop, as long as 
precipitate forms. By filtration a separation is effected of antimony am 
arsenic, since the latter passes into the filtrate. Arsenic may be thrown ou 
as yellow As 2 S 3 by H 2 S. Antimony remains in the precipitate with th 
metallic silver. Tin, if present, remains in the generator flask. 

III. KC10 3 in concentrated HC1 forms Cl 2 +CIO 2 , etc. The former act 
as a catalyzer, causing the arsenic to dissolve, as it forms the soluble H 3 AsO 
in the presence of an oxidizing agent. Nitric acid may be used in place c 
KC10 3 . 

Magnesium ammonium arsenate is somewhat soluble in water, hence th 
solution should be concentrated. A strong solution of NH 4 OH decrease 
the solubility of the arsenate. Precipitation is promoted by stirring 
Care must be taken, however, not to scratch the test tube with the rod, a 
this will give rise to an erroneous inference. 


On dissolving the precipitate in HC1 and adding H 2 S, a slow formatio: 
of the sulphides of arsenic, which is characteristic of that element, takes place 


1 








THE METALS 


79 


If AgN0 3 is added to a strictly neutral solution of arsenic, a brick-red 
icipitate, Ag 3 As0 4 , forms. If the sulphides have not been washed free of 

white AgCl will precipitate. Ammonium molybdate solution warmed to 

with an arsenic compound precipitates ammonium arseno-molybdate, 

How. . 

Platinum.—Platinic chloride is soluble in water; the addition of KC1 will 
crease its solubility. 1 A yellow color in the arsenic solution indicates its 
asence. With KI red K 2 Ptl 6 forms. 

Gold is precipitated in metallic form in the presence of ammonium oxalate 
len the solution is hot and slightly acid. The elements Se, Te, and Mo 
main in the solution in the form H 2 Se0 2 , H 2 Te0 3 , H 2 Mo0 4 . 

IV. The separation of antimony from tin depends, in the first method, 
ion the insolubility of Sb 2 S 3 in hot 8 per cent solution of HC1, while tin 
lphide is soluble. Cooling the filtrate and diluting precipitates tin as SnS 2 . 

In the confirmation of tin, zinc must not be allowed to dissolve completely, 

, in that case tin would also dissolve. The electromotive series is taken 
lvantage of here as it was in the case of antimony. In the latter case tin 

used in place of zinc to avoid the precipitation of any tin that might be 
resent. Should zinc be used, as in case of the second method of separation, 
n collects upon the zinc, and antimony upon the platinum foil. 

The iron nail reduces SnCl 4 to SnCl 2 , the latter oxidizing rapidly in the air 
> that it is necessary to filter the solution quickly into the HgCl 2 reagent. 

CLASSROOM REVIEW 

1. Study the Table of Reactions of the group in Part V, write the reactions 

2 What is the approximate strength of a cold saturated solution of HC1? 
/hat is the strength of a boiling solution and of the solution of the acid that 

istills over? 

3. What is the purpose of adding KC10 3 in section III, first mentioned? 

4. What are the following: tartar emetic, bronze, pewter, Paris green, 
cheele’s green, purple of Cassius? 

5. Name the metals belonging to the insoluble and the soluble H 2 S 

6. What compounds are formed by the action of (NH 4 ) 2 S X on the sul- 
ihides of arsenic, antimony and tin? 

7 Why is yellow ammonium sulphide used in place of the colorless 
mmonium sulphide for dissolving the sulphides of arsenic, antimony and 

1 See Potassium in Soluble Group. 




80 


QUALITATIVE ANALYSIS 


8. How can you distinguish between BiOCl and SbOCl? 

9. Why is a white precipitate produced when yellow ammonium sulphic 
is acidified? 

10. Why is copper soluble in nitric acid and insoluble in hydrochlor 
acid? (See Electromotive Series.) 

Mention another element of this group which does not dissolve in HC 

11. How is metallic bismuth distinguished from metallic lead? 

12. Why is it necessary to boil off free chlorine before applying the SnC 
test for mercury? 

13. Why is it advisable to destroy an oxidizing agent in a solution co 
taining the H 2 S group before precipitating the members of the group wii 
H 2 S? 

14. Why should the HC1 concentration not exceed 2.5 per cent of stroi 
HC1 in the solution from which the H 2 S group members are to be remove 
as sulphides? 

15. How may metallic antimony and metallic tin (in powder fora 
be distinguished from one another? 

16. Give a simple test by which the correct acidity of the solution co: 
containing the H 2 S group may be judged for sulphide precipitation. (Sp< 
test.) 

17. How may arsenous salts be distinguished from arsenic? If bol 
salts are present how would you prove it? 

18. Give the colors of the sulphides of the group—(A and B divisions 

19. Describe the Marsh arid the Gutzeit tests for arsenic. 

20. How would you distinguish between arsenic and antimony, deposit 
on platinum foil by means of the zinc or tin and platinum couple? 





AMMONIUM SULPHIDE GROUP 

Aluminum and Iron Groups, Iron and Zinc Groups , Group 3 


DESCRIPTIVE 

Common Elements—Precipitate as hydroxides by NH 4 OH : Aluminum, 
iromium, Iron. Precipitate as sulphides by (NH 4 ) 2 S : Cobalt, Manganese, 

ckel, Zinc (Iron). . 

Rarer Elements—Precipitate as hydroxides by NH 4 OH; Glucinum, 
rium, Neodymium, Praseodymium, Erbium, Lanthanum, Columbium, 
indium, Titanium, Thorium, Ytterbium, Yttrium, Zirconium, Precipitate 
sulphides by (NHi)sS : Gallium, Indium, Thallium, Uranium, Vanadium. 

3 Part VI. 

neral Characteristics. 

The elements of this group are precipitated either as sulphides 
as hydroxdes on addition of ammonium sulphide to their 
lutionsmade alkaline with ammonium hydroxide in the presence 
ammonium chloride. Three of the elements are precipitated 
hydroxides by NH 4 OH; namely, aluminum, chromium, and 
m. Advantage is taken of this fact by the Hydroxide Method 
separating these elements from the other members of the group, 
nmonium sulphide precipitates the elements in the form rf 
Iphides with the exception of chromium and aluminum, whic 
idergo hydrolysis and precipitate as hydroxides. 

idividual Chcractcristics . 

ALUMINUM 1 

Al, at.wt. 27.1; sp.gr. 2.683; m.p. 668.7°; b.p. 2200° C.; oxide AUO, 

Aluminum is a silver-white metal, having a hardness resembling alver, 
e pure metal being softer than the impure. The metal is ductile and malle- 
,le P irhls a tensile strength of over 12 tons to the square inch. The 

1 Also spelled aluminium. 

81 


82 


QUALITATIVE ANALYSIS 


element is a good conductor of heat and electricity. Its specific gravi 
is only To of that of copper. In the air the metal is coated over by a tl 
film of oxide, which prevents further action. In powdered form or in tl 
sheets at red heat it burns, forming the oxide AI 2 O 3 . Aluminum decompo; 
boiling water with evolution of hydrogen. It is an energetic reducing ag( 
at its melting-point, having a great affinity for oxygen at this temperatu 
Aluminum is trivalent; its salts are colorless. See list in Part V. 

Solution.—In dissolving substances containing aluminum keep in mind tl 
alumina, although ordinarily soluble in acids, is very difficult to disso 
when it is highly heated. It may be best dissolved in this case, by fus: 
with sodium carbonate or with acid potassium sulphate, followed by an a 
extraction. The metal is scarcely acted upon by nitric acid, but is read, 
soluble in the halogen acids and in hot concentrated sulphuric acids. 


DETECTION 

General Procedure.—The sample is brought into solution according 
one of the procedures outlined. Silica is removed by taking the solut 
to dryness, boiling the residue with hydrochloric acid and filtering. 1 
members of the hydrogen sulphide group are removed as usual with H 
the filtrate boiled to expel the excess of H 2 S, iron oxidized with nitric a( 
and aluminum, iron and chromium precipitated as hydroxides by addit 
of ammonium hydroxide in presence of ammonium chloride. On treat 
the precipitate with sodium peroxide, aluminum and chromium hydroxi< 
dissolve, whereas ferric hydroxide remains insoluble. Aluminum hydrox 
is precipitated by acidifying the alkaline solution with hydrochloric or nil 
acid, and neutralizing with ammonia; chromium remains in solution. 

The white gelatinous precipitate of aluminum hydroxide may be c 
firmed by adding a drop of cobalt nitrate solution and burning the filter. 1 
residue will be colored blue by the resulting aluminum cobalt compound. 

Sodium thiosulphate, Na 2 S 2 03 , added to a neutral or slightly acid solute 
containing aluminum precipitates aluminum hydroxide, upon boiling < 
solution. Sodium sulphite or ammonium chloride added in large excc* 
will also cause this precipitation. 

Alizarin S Test for Minute Amounts of Aluminum.—To about 5 ccA 
neutral or acid solution under examination add 1 cc. of a .1 per cent filter 
solution of alizarin S (the sodium salt of alizarin monosulphonic acid) 1 c 
ammonia until the solution is alkaline, as shown by the purple color. Isa 
boil for a few moments, allow to cool and then acidify with acetic acid. 4 
red-colored solution or precipitate remaining is evidence of aluminum. 






THE METALS 


83 


CHROMIUM 

, at.wt. 52.0; sp.gr. 6.92; m.p. 1620°; b.p. 2200° C.; oxides, Cr0 2 ; 

Cr 2 O 3, Cr0 3 

Chromium is a steel gray, shining metal, whose fracture shows large 
ratals. It is one of the hardest and most refractory of the metals. The 
“bides of chromium are harder than quartz. The metal, containing 1.5 to 
>er cent carbon can only be cut and polished by diamond dust. Chromium 
non-magnetic. It oxidizes slowly on heating, but burns in oxygen at 
lite heat. 

Chromium has three valences; the divalent chromium is basic in character 
d forms chromous compounds; the trivalent chromium is the form more 
nmonly known—it is also basic in character and forms chromic salts. In the 
xavalent form chromium acts as an acid, forming chromate. Chromium 
rives its name from the Greek XP<V a > meaning color, from the fact that 
compounds are colored. The aqueous solutions of chromium are green 
violet, chromates are yellow. Traces of the element color an aqueous 
ution. Chromic acid, Cr0 3 , is a familiar compound. A list of the more 
nmon compounds with their solubility, appearance and color is given 
Part V. 

Solution.—Powdered metallic chromium is soluble in dilute hydrochloric or 
phuric acid, it is only slightly soluble in dilute or concentrated nitric acid, 
is practically insoluble in aqua regia and in concentrated sulphuric acid. 

I rome iron ore is difficult to dissolve. It is important to have the material 
anely powdered form to effect a rapid and complete solution of the sample. 

agate mortar may be used to advantage in the final pulverizing of the 
>stance. Solution is generally accomplished by fusion with KHSO 4 , or 
, 2 C0 3 +KC10 3 , or NaHSOi+NaF, or Na 2 0 2 , or NaOH+KN0 3 . 

DETECTION 

| Chromium is precipitated by hydrogen sulphide and ammonium hydroxide 
! bluish-green, Cr(OH) 3 , along with the hydroxides of iron and aluminum 
1 embers of previous groups having been removed). The chromic compound 
| Dxidized to chromate by action of chlorine, bromine, sodium peroxide, or 
Irogen peroxide added to the substance containing an excess of caustic 
ali. The chromate dissolves and is thus separated from iron, which 
nains insoluble as Fe(OH) 3 . The alkali chromates color the solution 
low. 

Barium acetate or chloride added to a neutral or slightly acetic acid 
ution of a chromate precipitates yellow barium chromate, BaCrOi. Addi- 






84 


QUALITATIVE ANALYSIS 


tion of ammionium acetate to neutralize any free inorganic acid aids t 
reaction. 

Lead acetate produces a yellow precipitate with chromates, in neutral 
acetic acid solutions. 

Mercurous nitrate or silver nitrate gives red precipitates with chromat< 

Hydrogen peroxide added to a chromate and heated with an acid, su 
as sulphuric, nitric, or hydrochloric, will form a greenish-blue colored solutic 
Chromates are reduced by hydrogen peroxide in acid solution, the action bei 
reversed in alkaline solution. 

Reducing agents, hydrogen sulphide, sulphurous acid, ferrous sal 
alcohol form green chromic salts when added to chromates in acid solutk 

Ether shaken with a chromate to which nitric acid and hydrogen peroxi 
are added, is colored a transient blue. Oxygen is given off as the color fad 

HCr 0 4 + 3 HN 03 = Cr(N0 3 )3+2H 2 0+0 2 

Diphenyl carbazide test.—To 5 cc. of the solution containing chromii 
as chromate, 2 drops of hydrochloric or acetic acid are added, and 1 drop 
an acetic acid solution of diphenyl carbazide (0.2 gram CO(NHNH*C c H 
is dissolved in 5 cc. glacial acetic acid and diluted to 20 cc. with ethyl alcohc 
A violet pink color is produced in presence of a chromate. Less th 
0.0000001 gram chromium may be detected. 

Chromic salts are bluish green; chromic acid is red; chromates, yellc 
bichromates, red; chrome alum, violet. 

The powdered mineral, containing chromium, when fused with sodii 
carbonate and nitrate, produces a yellow-colored mass. 

COBALT 

Co, at.wt. 68.97; sp.gr. 8.7918; m.p. 1478°; b.p. unknown; Oxides, Co 3 ( 

C 02 O 3 , CoO, C 0 O 2 

Cobalt is a white, tough, ductile metal and like iron, is temporarily mf 
netic. It does not change in moist air. At a red heat it decomposes wat 
The metal dissolves slowly in HC1 and in H 2 S0 4 and rapidly in HN0 3 . Most 
the cobalt alloys dissolve in nitric acid. Some of the alloys (cobalt-chromii 
alloys) require fusion with sodium peroxide followed by acid treatment 
obtain their solution. 

Cobalt has two valences divalent and trivalent, forming cobaltous a 
cobaltic compounds. Most of the cobaltous compounds appear red in soi 
tion or as salts with water of crystallization, and blue when anhydroi 





THE METALS 


85 


rhe concentrated solutions in presence of HC1 are blue. A list of salts 
s given in Part V. 

DETECTION 

General Procedure.—After the removal of the elements precipitated by 
lydrogen sulphide from acid solution, a little nitric acid is added to the 
solution to oxidize to the ferric state any ferrous salts which may be present, 
md ammonia is added until its odor is distinctly perceptible, to precipitate 
ron, aluminum and chromium. This precipitate is removed by filtration 
md hydrogen sulphide passed through the ammoniacal solution to precipitate 
iobalt, nickel, manganese and zinc. After collecting this precipitate it is 
vashed thoroughly with cold hydrochloric acid of approximately 1.035 
specific gravity, to remove manganese and zinc. A small quantity of the 
•esidue is fused with borax in the loop of a platinum wire. A blue color 
n the cold bead indicates cobalt. This test is masked by the presence of 
arge quantities of nickel. In this case the residue is dissolved in hydrochloric 
icid to which a few drops of nitric acid have been added and the solution 
;vaporated to dryness. The residue is redissolved in water, acidified with 
lydrochloric acid and the cobalt precipitated with a hot solution of nitro-beta- 
laphthol in 50 per cent acetic acid. A brick-red precipitate indicates 
;obalt. 

Potassium sulphocyanate, KCNS, produces a red color with cobalt. 
\lcohol and ether are added to this solution and shaken. The ether layer is 
jolored blue by cobalt. If iron is present a solution of sodium thio-sulphate, 
STa 2 S 2 0 3 , is added until the red color disappears, the solution filtered and then 
;reated with the alcohol-ether mixture. 

Potassium Nitrite, KN0 2 , added to a neutral or slightly acid solution con- 
aining acetic acid, will precipitate cobalt as a yellow complex nitrite having 
i he formula K 3 Co(N0 2 )6. 

, Dicyandiamidine sulphate and sodium hydroxide solution added to a cobalt 
solution to which ammonia has been added until the color is distinctly dis¬ 
cernible, and containing from 10 to 20 cc. of 10 per cent sugar solution, will 
Change the color of the solution to red or reddish violet. If large quantities 
>f nickel are present the color will be yellow or reddish yellow, after which 
he nickel will separate out in brilliant crystals, leaving the cobalt in solution, 
Coloring it as described above. 

Ammonium sulphocyanate concentrated solution added to a cobaltous 
! olution colors it blue. On dilution this becomes pink. Amyl alcohol or a 
I mixture of amyl alcohol and ether 1 : 1, added to this and shaken, extracts this 
i due compound. Iron sulphocyanate, Fe(CNS) 3 , likewise colors the ether- 
1,lcohol extract red, which may mask the cobalt blue. By addition of sodium 






86 


QUALITATIVE ANALYSIS 


carbonate solution ferric hydroxide precipitates, while the cobalt color will 
remain after this treatment. 

IRON 

Fe, at.wt. 66.84; sp.gr. 7.86-7.88; m.p. pure, 1630°, wrought, 1600°, white 
pig, 1076°, gray pig, 1276°, steel, 1376°; b.p. 2460° C.; oxides FeO, 
Fe 2 0 3 , Fe 3 0 4 . 

Iron is a crystalline, silver-white metal, soft and easily welded, and mal¬ 
leable. It rusts in moist air; in finely divided form it decomposes water with 
the evolution of hydrogen at ordinary temperatures. With dilute acids iron 
forms ferrous salts, liberating hydrogen; with concentrated sulphuric acid 
it forms ferric sulphate, liberating S0 2 ; in hot concentrated nitric acid it 
forms ferric nitrate with the liberation of NO. Dipped in cone, nitric acid 
and washed, the iron becomes “ passive,” and is not further acted upon by the 
acid, and does not precipitate copper from a solution of its salts. Iron forms 
three series of compounds: the bivalent—ferrous compounds are white or 
green, similar to the salts of the magnesium group; the trivalent—ferric salts 
are very stable compounds and are brown or yellow; the haxavalent iron 
forms ferric acid, known only in combination. 

Solubility.—The following facts regarding solubility should be remembered: 
The element is soluble in hydrochloric acid and in dilute sulphuric acid, forming 
ferrous salts with liberation of hydrogen. It is insoluble in concentrated, 
cold sulphuric acid, but is attacked by the hot acid, forming ferric sulphate 
with liberation of S0 2 . Moderately dilute, hot nitric acid forms ferric nitrate 
and nitrous oxide; the cold acid gives ferrous nitrate and ammonium nitrate 
or nitrous oxide or hydrogen. Cold, concentrated nitric acid forms “ passive 
iron, which remains insoluble in the acid. The oxides of iron are readily 
soluble in hydrochloric acid, if not too strongly ignited, but upon strong 
ignition the higher oxides dissolve with Extreme difficulty. They are readily 
soluble, however, by fusion with acid potassium sulphate followed by an 
acid extraction. Silicates are best dissolved by hot hydrochloric acid con¬ 
taining a few drops of hydrofluoric acid or by fusion with sodium and potas¬ 
sium carbonates, followed by hot hydrochloric acid. The chloride, sulphate 
and nitrate salts of iron are soluble in water. .Sulphide ores and material 
containing organic matter should be roasted and then dissolved in hydro¬ 
chloric acid for the test solution. 

DETECTION 

Ferric Iron. The yellow to red color in rocks, minerals, and soils is gen¬ 
erally due to the presence of iron. 






THE METALS 


87 




Hydrochloric acid solutions of iron as ferric chloride are colored yellow. 

Potassium or ammonium sulphocyanate produces a red color with solutions 
ontaining ferric iron. Nitric acid and chloric acid also produce a red color 
vith potassium or ammonium sulphocyanate. This color, however, is 
lestroyed by heat, which is not the case with the iron compound. The red 
:olor of ferric iron with the cyanate is destroyed by mercuric chloride and by 
ihosphates, borates, certain organic acids, and their salts, e.g., acetic, oxalic, 
artaric, citric, racemic, malic, succinic, etc. 

Potassium ferrocyanide, KiFe(CN)6, produces a deep blue color with 

erric salts. 

Salicylic acid added to the solution of a ferric salt containing no free mineral 
icid gives a violet color. Useful for detecting iron in alum and similar 
products. 

Ferrous Iron. Potassium Ferricyanide, K 3 Fe(CN) 6 , gives a blue color 
vith solutions of ferrous salts. 

Distinction between Ferrous and Ferric Salts. 

KCNS gives red color with Fe + + + and no color with Fe + + . 

K 3 Fe(CN) 6 gives a blue color with Fe+ + and a brown or green with 

^0+ . 

NH 4 OH, NaOH or KOH precipitates red, Fe(OH) 3 with Fe + + + and 
vhite, Fe(OH) 2 with Fe+ + , appearing green in presence of air. 

Sodium peroxide produces a reddish-brown precipitate of Fe(OH) 3 with 
lither ferrous or ferric salt solutions, the former being oxidized to the higher 
valence by the peroxide. Chromium and aluminum remain in solution, if 
present in the sample. 


MANGANESE 

Mn, at.wt. 54.93; sp.gr. 7.42; m.p. 1260°; b.p. 1900° C; oxides, MnO, 
MmOi, (Mn.jO, ignition in air), Mn0 2 , Mn0 3 , Mn.O,. 

Manganese is a grayish white, hard, brittle metal, which oxidizes in moist 
ir It decomposes boiling water, liberating hydrogen. It is not magnetic, 
i'our valences are known: divalent form in manganous compounds, tn valent 
n manganic compounds, hexavalent in manganic acid salts, and heptavalent 
a permanganic compounds. A list of compounds of manganese may be 

° U Solubility.—The metal dissolves in dilute acids. The oxides and 
lydroxides of manganese are soluble in hot hydrochloric acid. Manganese 
,ride is soluble in nitric acid and in sulphuric acid; the dioxide is msoluble 
n* dilute or concentrated nitric acid, but dissolves m hot concentrated 
sulphuric acid and in hot hydrochloric acid. 







88 


QUALITATIVE ANALYSIS 


DETECTION 

General Procedure.—In the usual course of analysis manganese is found 
in the filtrate from the hydroxides of iron, aluminum and chromium, the pre ( 
vious groups having been removed with hydrochloric acid, hydrogen sulphidd 
and ammonium hydroxide in presence of ammonium chloride. Manganese 
cobalt, nickel and zinc are precipitated as sulphides in an ammoniacal solution 
The sulphides of manganese and zinc are dissolved by cold dilute hydro 
chloric acid, H 2 S expelled by boiling and manganese precipitated as the 
hydroxide by addition of potassium hydroxide in sufficient amount to dissolve 1 
the zinc (sodium zincate). Manganese is now confirmed by dissolving this ] 1 
precipitate in nitric acid, adding red lead or lead peroxide to the strong nitric ; 
acid solution then heating and boiling. A violet-colored solution is pro ' 
duced in presence of manganese. Chlorides should be absent. 

Sodium bismuthate added to a cold dilute nitric acid solution (3:1, sp.gr 
1.135) containing manganese, produces the violet-colored solution of perman¬ 
ganic acid. The test is extremely delicate, 0.00000 > gram manganese wilt 
give an appreciable color in 50 cc. of solution. Chlorides should be absent 
(Remove by adding AgN0 3 and filter.) 

Manganese in soil, minerals, vegetables, etc., is detected by incinerating 
the substance, treating the ash with nitric acid and taking to dryness, the 
residue is taken up with water and the mixture filtered. To the filtrate is 
added a few cc. of 40 per cent ammonium persulphate and a little 2 pei 
cent silver nitrate solution. A pink color is produced in presence of man¬ 
ganese. 

Manganese compounds heated with borax in the oxidizing flame produce 
an amethyst red color. The color is destroyed in the reducing flame. 

Fused with sodium carbonte and nitrate on a platimum foil manganese 
compounds produce a green-colored fusion (“ Robin egg blue ”). 

NICKEL 

Ni, at.wt. 68 . 68 ; sp.gr. 8.6-8.9; m.p. 1462°C.; oxides, NiO, Ni 2 0 3 , Ni 3 0 4 

Nickel is a silver-white, tough, ductile metal, which is not oxidized in 
the air. At red heat it decomposes water. Its compounds are like those of 
cobalt. The metal is magnetic. With water of crystallization or in solution 
nickelous salts are green, in the anhydrous form they are yellow. The green 
solution becomes colorless in presence of cobalt (3 Ni : 1 Co). 

The determination is required in the analysis of ores, metallic substances, 
alloys, etc. 

Solubility.—The element is soluble in dilute nitric acid, slightly soluble 





THE METALS 


89 


n hydrochloric acid and in sulphuric acid. The materials in which nickel 
i(l*ccurs ordinarily may be brought into solution by treatment with acids. 

& Certain refractory ores and alloys require fusion with sodium carbonate or 
potassium bisulphate before treating with acid. See List of Salts in Part V. 

DETECTION 

General Procedure.—After bringing the sample into solution silica is 
•emoved, if present, in the usual manner, by evaporating the solution to dry- 
less in the presence of an excess of hydrochloric acid, dissolving the residue 
ind boiling with hydrochloric acid and filtering off the silica. Hydrogen 
sulphide is then passed through the solution to remove the elements precipi¬ 
tated by this reagent. The filtrate from this precipitation is then boiled 
bo expel the excess of hydrogen sulphide and a little nitric acid added to 
Dxidize any ferrous iron to the ferric state. Ammonium hydroxide is then 
added to precipitate iron, aluminum and chromium. Cobalt, nickel, man- 
^ ganese and zinc are precipitated from the filtrate by adding a solution of 
colorless ammonium sulphide or by passing hydrogen sulphide through the 
ammoniacal solution. Manganese and zinc are separated from the precipitate 
by washing with cold hydrochloric acid of about 1.035 sp. gr. A small quantity 
of the precipitate is fused with borax in the loop of a clean platinum wire. A 
green color in the cool bead indicates nickel. Fairly small quantities of cobalt 
interfere with this test, so if the bead is colored blue it will be necessary to 
make further tests for nickel. 

Dimethylglyoxime will precipitate nickel as oxime from an acetic acid 
solution containing sodium acetate, in this manner separating it from cobalt, 
manganese and zinc. After precipitating iron, aluminum and chromium and 
filtering them off, the solution is slightly acidified with hydrochloric acid, then 
is neutralized with sodium hydroxide, and acidified with acetic acid. A solu¬ 
tion of dimethylglyoxime is added, when nickel, if present, will be precipitated 
as a flocculent red precipitate. Precipitation takes place readily in an am¬ 
moniacal solution. Traces of nickel give a pink color with the reagent. 

Nickel may be detected in the presence of cobalt by adding a solution of 
sodium hydroxide to the solution of cobalt and nickel until a slight precipitate 
is formed, then somewhat more potassium cyanide than is necessary to redis- 
solve the precipitate and finally two volumes of bromine water. Warm 
gently and allow to stand for some time. If a precipitate of nickel hydroxides 
separates, filter, wash and test with the borax bead. 

Nickel may also be detected in the presence of cobalt by precipitating the 
cobalt as nitrite, and then precipitating the nickel as hydroxide with sodium 
hydroxide and bromine water and testing the precipitate with the borax bead. 



90 


QUALITATIVE ANALYSIS 


Alpha benzildioxime added to an ammoniacal solution of nickel precipitates 
an intensely red salt having the composition C 2 8 ll 2 2N 4 0 4 Ni. This precipitate 
is very voluminous. Silver, magnesium, chromium, manganese and zinc do 
not interfere with this reaction. 


ZINC 

Zn, at.wt. 65.37; sp.gr. 6.48 to 7.19; m.p. 419°; b.p. 920°; ZnO oxide. 

Zinc is a bluish white crystalline metal; brittle at ordinary temperatures; 
malleable at 100°; brittle at 200°. Its hardness is between that of tin and 
copper. At boiling temperature the metal bums in the air with a pale greenish- 
blue flame, forming zinc oxide. In moist air the metal is coated with a stable 
carbonate which acts as a protection against further action. Zinc is used in 
galvanizing iron to protect it from corrosion by oxidation, in this respect 
acting more perfectly than tin. Zinc forms an important constituent in a 
number of alloys. At red heat zinc decomposes water; in powdered form, it 
acts on cold water. 

Solubility.—Pure metallic zinc is not readily attacked by acids, but a 
trace of impurity acting as a catalyzer causes it to dissolve. The metal dis¬ 
solves in alkalies, impurities assisting the reaction. Cold dilute HN0 3 
dissolves Zn with evolution of N 2 0 and NO. Strong HN0 3 has only a slight 
action, the nitrate being sparingly soluble in HN0 3 . Hot cone. H 2 S0 4 
dissolves Zn with evolution of S0 2 . 

Salts.—All zinc salts are soluble in NaOH, KOH, and NH 4 OH, except 
ZnS. Zn 2 Fe(CN) 6 is insoluble in NH 4 OH and in HC1. ZnS is insoluble in 
dilute HC1. The sulphide, basic carbonate, phosphate, arsenate, oxalate, 
and ferrocyanide of zinc are sparingly soluble in water. A list of compounds 
of zinc may be found in Part V. 


DETECTION 

General Procedure.—After the removal of the HC1 and H 2 S groups, 
Fe, Al, and Cr may be precipitated as hydroxides, or as basic acetates. Zn 
is now precipitated with Co, Ni, and Mn from an ammoniacal solution by 
H-S. The precipitated sulphides are treated with cold dilute HC1, where¬ 
upon Zn and Mn dissolve as chlorides. After expelling H 2 S by boiling, Zn 
is changed to the soluble Na 2 Zn0 2 by an excess of NaOH, which precipitates 
Mn as the hydroxide. From the alkaline filtrate white ZnS is precipitated 
by H 2 S. 

The finely powdered material, when heated on charcoal in the reducing 
flame of a blowpipe, gives an incrustation, yellow when hot—white when cold. 








THE METALS 


91 


)n moistening with cobalt nitrate solution and reigniting, the mass is greenish- 
fellow. Materials containing about 5 per cent Zn will give positive tests. 

In case the material is of interest, only if it carries higher than several 
3 er cent of zinc, a shorter and easier wet test is to bring the material into 
solution by means of hydrochloric or nitric acid, add bromine water and then 
precipitate iron, aluminum and manganese with ammonia and bromine, 
filter, wash and make the filtrate acid with hydrochloric acid, 10 cc. excess 
being added for each 100 cc. of solution. Now potassium ferrocyanide is 
added, whereupon zinc gives the characteristic precipitate Zn 2 Fe(CN) 6 . Cop¬ 
per interferes and if present must be separated with hydrogen sulphide. 

In case manganese and copper are known to be absent, a still shorter test 
may be used: To the solution of the zinciferous material add 2 or 3 grams of 
citric acid per 200 cc. solution, then make ammoniacal, add ferrocyanide— 
a white precipitate indicates zinc. 

Alkali hydroxides precipitate Zn(OH) 2 , soluble in excess. Ammonium 
Sulphide and also Hydrogen Sulphide precipitate white ZnS from neutral or 
acetic acid solutions. The sulphide is insoluble in KOH. 




• 92 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Chemical Reaction of the Ammonium Sulphide Group 

A. Action of a Phosphate.—Ascertain the effect of a soluble 
phosphate, e.g., Na 2 NH 4 P 04 , on, first, acid solutions, then 
alkaline solutions containing the ions of iron, aluminum, chro¬ 
mium, cobalt, nickel, manganese, zinc, barium, calcium, strontium, 
magnesium, using separate solutions of each. Do the precipitates 
formed in the alkaline solutions (NH 4 OH) dissolve on the addi¬ 
tion of ammonium acetate and free acetic acid? Does an excess 
of a solution of an iron salt remove the phosphate ion? 

B. Organic Matter.—Use a sugar solution and note the 
effect on the precipitation of the members of the (NH 4 ) 2 S group. 

C. Oxalic Acid.—What elements of the list above mentioned 
are precipitated in presence of ammonium oxalate by addition of 
NH 4 OH? 

ALUMINUM A1+ + + 

Use a solution of A1C1 3 or K 2 A 1 2 (S 04 ) 3 . 

^ 1. To a portion add NH4OH in slight excess. 

Reaction (a): A1C1 3 +3NH 4 OH = J. Al(OH) 3 white gelatinous +3NH 4 C1. 

Note. In practice it is customary to add NH 4 C1 to prevent precipitation 
of Mg, and Zn. See Introduction, Solubility Product. What effect has this 
salt on Al(OH) 3 ? 

The precipitate is soluble in a 2.5 per cent HC1 solution 
(sp.gr. 1.2). 

(6) A1 (OH) 3 -f- 3HC1 = A1C1 3 +3H 2 0. 

2. To another portion add an alkali acetate solution. Di¬ 
lute largely and heat to boiling. The precipitate in the hot 
solution is basic aluminum acetate, soluble in acids. 

Reactions.— (a) A1C1 8 +3NH 4 C 2 H 3 0 2 = A1(C 2 H 3 0 2 ) 3 +3NH 4 C1. 

(b) Hot solution A1(C 2 H 3 0 2 ) 3 +H 2 0 <=* j A1(0H)(C 2 H 3 0 2 ) 2 +HC 2 H 3 0j. 



THE METALS 


93 


3. Pass in H 2 S into a portion: 

(a) In acid solution no precipitate forms. 

( 1 b ) Add NH 4 OH and H 2 S or (NH 4 ) 2 S. 

Reaction.— (a) A1C1 3 +3(NH 4 ) 2 S = Al 2 S 3 +6NH 4 Cland 
AI2S3+6H2O = |-2A1(0H) 3 + T 3H a S. 

Note. —The hydroxide precipitates, not the sulphide, since the latter is 
ydrolyzed'by water. 

4. Test the solubility of Al(OH) 3 in an excess of NaOH or 
£OH. Note that the hydroxide dissolves. Aluminum interact- 
ng with the strong base to form the soluble sodium aluminate. 
See Introduction—Amphoteric Electrolytes. 

Reaction. —Al(OH) 3 H-3NaOH = Na 3 A10 3 +3H 2 O—. 

5. Neutralize the solution obtained in No. 4 with an acid; 
U(OH) 3 again precipitates. 

Reaction. —Na 3 A10 3 -{-3HCl = i Al(OH) 3 H-3NaCl. 

The precipitate dissolves with an excess of acid according 
bo the reaction (b) in No. 1. 

6. Confirmatory test for aluminum is made to distinguish it 
from silica, if present. Dissolve the precipitate Al(OH) 3 in 5 cc. 
Df HN0 3 (sp. gr. 1.2). (Use only a portion if the precipitate is 
large.) Add 4-5 drops of N/100 Co(N0 3 ) 2 . 

Evaporate the solution to dryness, then add a drop or so of 
water, and soak up the liquid on a small piece of filter paper. 
Roll up the paper and ignite in a flame, holding the paper in the 
spiral of a platinum wire. Drop the ash in a crucible and heat 
to destroy the carbon. A blue residue in the ash is due to an 
aluminum cobalt compound (Notes). 

7. Alizarin S test. See under the descriptive portion for Alum¬ 
inum “ Detection/’ page 82. 




94 


QUALITATIVE ANALYSIS 


CHROMIUM 

Under the description for this element it was learned thal 
in the divalent and trivalent forms, chromium was basic ir 
character, forming chromous and chromic salts with acids; anc 
that in the hexavalent form chromium acted as an acid forming 
with bases the familiar compounds known as chromates. The 
two latter forms will be considered, chromous compounds being 
of less importance. 

Examples (a) CrO-f-2HCl = CrCl 2 +H 2 0 Chromic salt. 

(b) Cr 2 03 + 6 HC 1 ^ = CrCl 3 -f3H 2 0 Chromous salt. 

(c) 3Cr0 3 +6K0H = 3K a Cr0 4 +3H 2 0 Chromate. 

For the tests use a choice of the following: 

Chromic Salts—CrCl 3 , Cr 2 (S0 4 ) 3 1 , Cr(N0 3 ) 3 , Cr 2 (S0 4 ) 3 ; Chromates : 
Na 2 Cr0 4 , K 2 Cr0 4 , or Cr0 3 . 

Formation of Chromates from Chromic Salts by Oxidation. 
Requisites.—An alkaline solution of a chromic salt and a suitable 
oxidizing agent. (H 2 0 2 , Na 2 0 2 , KMn0 4 , Br, Cl, I, etc.) 

Example A2CrCl 3 + lONaOH+30 = 2Na 2 CrO 4 +6NaCl -f 5H 2 0. 

8. To a solution of chromic salt, CrCl 3 , add sufficient NaOH 
to precipitate the hydroxide (Cr(OH) 3 ) and cause its solution 
(Na 3 Cr0 3 ). Now add hydrogen peroxide, H 2 0 2 , and heat the 
solution to boiling. A yellow color will be evident, due to the 
formation of sodium chromate. 

Reaction.— 

2 CrCl 3 +1 ON aOH + 3H 2 0 2 = 2Na 2 Cr0 4 (yellow)+6NaCl+8H 2 0. 

Note— The result may be accomplished by addition of sodium peroxide 
alone in place of NaOH and H 2 0 2 , since Na 2 0 2 in presence of water decom¬ 
poses, yielding NaOH and O. 

1 The ignited chloride and sulphate salts are insoluble in water and in acids. 




THE METALS 


95 


Formation of Chromic Salt from a Chromate. Requisites.— 

An acid solution of a dichromate (chromate+acid = dichromate x ) 
md a reducing agent. (H 2 S, S0 2 , HC1 concentrated, HI, 
SO 2 , etc.) 

Example B— 2K 2 Cr0 4 +2HN0 3 = K 2 Cr 2 0 7 +2KN0 3 +H 2 0 and 
K 2 Cr 2 0 7 +H 2 S 0 4 -f 3 SO 2 = Cr 2 (SO 4 ) 3 +K 2 SO 4 +H 2 0. 

9. Acidify a solution of potassium chromate, K 2 Cr 04 , with 
HC1 added in excess. Note the change of color from yellow to 
orange red due to the formation of the dichromate. Now pass 
in H 2 S gas (SO 2 may be used if preferred). Note the change of 
color from orange to green, due to the reduction of the dichromate 
to the chromic salt. 

Reactions.—(a) K 2 Cr0 4 +2HCl = K 2 Cr 2 0 7 +2KCl+H 2 0. 

( 6 ) K 2 Cr 2 0 7 +8HCl+3H 2 S = 2 CrCl 3 + 2 KCl + 1 3S+7H 2 0. 

Note. —The formation of sulphur is shown by the cloudiness of the solu¬ 
tion. 

Hydrochloric acid alone will reduce the chromate if present in sufficient 
amount. 

K 2 Cr 2 0 7 +14HC1 = 2CrCl 3 +2KC1 4- 13C1 2 +7H 2 0. 

In the regular course of complete analysis of a mixture of 
compounds chromium appears as chromic chloride in the filtrate 
from the H 2 S group. The compound is precipitated as a hydrox¬ 
ide, then, oxidized to the chromate form and there identified. 

10. (a) Add to a solution of chromic salt, CrCl 3 , a slight 
excess of NH 4 OH and boil until only a faint odor of NH 3 remains. 
Note the color of the precipitate. 

Reaction.— CrCl 3 +3NH 4 OH = Cr (OH) 3 (green) +3NH 4 C1. 

Note. —Slightly soluble in excess of NH 4 OH with formation of violet solu¬ 
tion from which Cr(OH ) 3 is precipitated on boiling. 


1 A dichromatic+an alkali forms a chromate. 


96 


QUALITATIVE ANALYSIS 


(6) Test the solubility of Cr(0H)3 in a solution of a stroni 
base—NaOH or KOH. The hydroxide dissolves, forminj 
Na3Cr(>3 or K^CrCV 

Reaction.—Cr(OH) 3 +3NaOH *=> Na 3 Cr0 3 +3H 2 0. 

Boiling the chromite solution reverses the action, causing Cr (OH) 3 to pre 
cipitate. 

(c) Does the addition of NH 4 CI cause solution of Cr(OH )3 

11. To a solution of chromic salt, made alkaline with NH 4 OH 
add a few cc. of (NILO 2 S or pass in H 2 S gas. Note the color o 
the precipitate. 

Reactions.—(a) CrCl 3 +3(NH 4 ) 2 S = Cr 2 S 3 +6NH 4 Cland 

(6) C r2 S 3 +6H 2 0 = 1 2Cr(OH) 3 (green ppt.) + T 3H 2 S. 

Compare the reaction with Experiment 3 under aluminum. 

12. Collect the chromic hydroxide precipitate, obtained ii 
Experiment 3 or 4, on a filter, transfer to a porcelain dish, dissolve 
in a few cc. of cold 2N-HC1 (sp.gr. 1.035), make alkaline witl 
NaOH and add Na202 in small portions until about 2 grami 
has been added. Note whether a precipitation takes place 
Heat, until effervescence ceases, to decompose the peroxide 
What change has taken place in the chromic salt? Consuli 
Reaction in Experiment 8. 

Note .—NaOH precipitates Cr(OH) 3 , soluble in excess with formatioi 
of Na 3 Cr0 3 from which solution Cr(OH) 3 is precipitated on boiling (distinctiv< 
from aluminum). 

13. Acidify a portion with strong HN0 3 (sp. gr. 1.42) anc 
then make alkaline with NH 4 OH. Does a precipitate form* 
What changes take place by acidifying the chromate and agair 
making alkaline? Consult Experiment 9. 

Confirmatory Tests for Chromium 

14. Add sufficient acetic acid to make the solution, remaining 
from Experiment 12, slightly acid. Now add a solution either or 



THE METALS 


97 


ead acetate or barium acetate. Note the precipitate is 
fellow. 

Reaction. — (a) Na 2 Cr 04 +Pb(C 2 H 3 0 2 ) 2 = I PbCr0 4 yellow +2NaC 2 H 3 0 2 . 

(6) Na 2 Cr 04 +Ba(C 2 H 3 0 2 ) 2 = 1 BaCrCL yellow 
-j-2NaC 2 H 3 0 2 . 

15. Oxidation Test of a Chromate may be made as follows: 
Filter and dissolve the precipitate by pouring repeatedly over it 
5-10 cc. HNO3 (1.07). To the cold filtrate in a test tube add about 
2 cc. of ether and 1 cc. of a 3 per cent solution of H 2 O 2 . Shake 
well. A blue color is imparted to the ether layer, probably due 
to the formation of HCrCU, perchromic acid. 

16. Reduction Test.—Solutions of chromates are yellow; the 
yellow color changes to orange red by additions of acids 
( = M 2 Cr 2 (> 7 ) and is restored by adding alkalies ( = M2CrC>4). 
The acid solution treated with a reducing agent (H 2 S, SO 2 , strong 
HC1, etc.) changes from an orange red to green. Heating assists 
the reduction. 

Note .—The chromate yellow is restored by making the solution alkaline 
with NaOH or KOH and adding Na 2 0 2 . 


IRON, Fe++, Fe+ + + 

In the usual course of analysis iron is present in the filtrate 
from the H 2 S groups in the ferrous form. (Experiment 26, Note, 
under Ferric Iron.) In the confirmatory tests in its detection 
iron exists in the solution as a ferric salt. The student should 
become familiar with characteristic of both forms of iron, by 
laboratory experiments, testing ferrous and ferric salts in solu¬ 
tion with the reagents used in separating iron from other elements 
of its group and in establishing its identity. 

Ferrous Iron.—In the following tests 5 cc. portions of the 
ferrous solution may be used. 


98 


QUALITATIVE ANALYSIS 


17. Preparation of the Ferrous Solutions.—Place 150 cc. of di 

tilled water in an Erlenmeyer flask, add a few crystals of FeSC 
or (NH 4 ) 2 Fe(S 04 ) 2 , then add 10 cc. of dilute H 2 SO 4 (1 : 1) an 
several pieces of bright pure iron wire (rust removed by sane 
paper). Close the flask with a stopper through which passe 
a glass tube connected with a rubber tube, 2 inches long, close 
at the upper end and having a slit ^-inch long cut through ii 
wall between the glass tube and the closed end. (Bunsen valve 
This valve permits the passage of gas from the flask, but prevenl 
an intake of air. Gently heat the solution until gas bubble 
begin to evolve. By this procedure any ferric iron, which ma 
be present in the ferrous salt, is reduced. 

Reactions.— Fe 2 (SO 4 ) 3 +H 2 = 2FeS0 4 +H 2 S0 4 . 

18. Add a few drops of NH 4 OH to one portion in sufficien 
amount to give the solution an odor of NH 3 . Observe the color 
of the precipitate. Rapid oxidation by the air changes Fe(OH) s 
white, to green and finally red Fe(OH) 3 . 

Reactions.— (a) FeS0 4 +2NH 4 0H = 1 Fe(0H) 2 -|-(NH 4 ) 2 S0 4 . 

(b) 2Fe (OH) 2 +0 (air) + H 2 0 = 2Fe (OH) 3 . 

Test the solubility of the precipitate in HC1. 

Reaction.— Fe(OH) 3 +3HC1 FeCl 3 +3H 2 0. 

19. (a) Into a slightly acid solution of ferrous salt pass H 2 £ 
gas. Does a precipitate form? 

(6) Make the solution thus treated ammoniacal, passing ir 
more H 2 S. 

Reaction.— 

FeSO ( +2NH,OH+H 2 S = | FeS (blackppt.)+(NH,) 2 S0,+2H 2 0. 

(c) Test the solubility of FeS in dilute HC1 (2.5 per cent 
solution—sp.gr. 1.2). 

Reaction.— FeS+2HCl = FeCl 2 + THaS. 


THE METALS 


99 


20. To a portion of ferrous solution add a solution of potassium 
srrocyanide. The white K 2 Fe ++ [Fe(CN)o] which would form 
a absence of air, is rapidly oxidized by air to Fe 4 [Fe(CN)e] 3 , 
Prussian blue. 

Reaction.— 4F eSO 4 +3K 4 Fe (CN) 6 +2H 2 SO 4 +O 2 (air) = 
i Fe 4 [Fe(CN) 6 ] 3 , blue ppt.+6K 2 S0 4 +2H 2 0. 

21. To another portion add potassium ferricyanide solution. 
?he blue precipitate is known as Turnbull’s blue. 

Reaction.—3FeS0 4 +2K 3 Fe(CN) 6 = j Fe 3 [Fe(CN) 6 ] 2 , blue ppt.+3K 2 S0 4 . 

The precipitate is insoluble in HC1, but is decomposed by a 
ixed alkali as follows: 

2Fe 3 [Fe(CN) 6 ] 2 +16K0H+H 2 0+0 = 1 6Fe(OH) 3 +4K 4 Fe(CN)«. 

22. Potassium thiocyanate or ammonium thiocyanate has 
10 action on ferrous solutions. (Ferric iron produces a red color 
vith KCNS.) Prove this by testing a portion of the ferrous 
lolution with the reagent. 

33. Oxidation of Ferrous Iron.—Boil the remainder of the 
errous solution and add strong nitric acid drop by drop until 
here is no further darkening of the solution with addition of 
nore HNO 3 . If a drop of this solution is placed on a white tile 
>r on paraffined white paper and a drop of fresh K 3 Fe(CN )6 
olution (a crystal of the salt in 10 cc. H 2 O) no blue color will 
esult, if the oxidation is complete. 

Reaction— 6FeS0 4 +2HN0 3 +3H 2 S0 4 = 3Fe 2 (S0 4 ) 3 + T 2N0+4H 2 0. 

Oxidation of ferrous chloride with nitric acid causes a color 
ihange from colorless through brown and finally an amber yellow. 

3FeCl 2 +HN0 3 +3HCl = 3FeCI 3 + T N0+2H 2 0. 

Iron may be oxidized by KCIO3, H 2 O 2 , K 2 Cr 207 , KMn 04 . 
rhe last two reagents are used in the quantitative determination 
>f iron. 


100 


QUALITATIVE ANALYSIS 


Ferric Iron.—The tests made with ferrous iron using the soli 
tion made in Experiment 17 or a fresh solution of ferric chlorid 
FeCl 3 , should be repeated following the order given below. 

In the process of analysis, iron is generally present as a chlorid 
The reactions will be written with the supposition that this sa 
is used. 

24. (a) Add NH 4 OH to a solution of ferric salt. 

Reaction.— FeCl 3 +3NH 4 OH = Fe(OH) 3 , reddish brown ppt. +3NH 4 C1. 

( 6 ) Test solubility of Fe(OH )3 in HC1 and in dilute HNO 
Write out the reaction. 

(c) Test the solubilty of Fe(OH ) 3 in NaOH or KOH solutioi 

(d) Does the addition of NH 4 C1 cause the hydroxide t 
dissolve? 

25. Add sodium or ammonium acetate to a solution of ferri 
salt, slightly acid. 

FeCl 3 +3NH 4 C 2 H 3 0 2 = i Fe(C 2 H 3 0 2 ) 3 +3NH 4 Cl. 

26. Pass in H 2 S. 

(a) Into an acid solution of ferric salt containing 2.5 c< 
cone. HC1 per 100 cc. 

Is the reaction evident? Does a precipitate form? 

(See Experiment 27 following). 

(b) Add NH4OH and H2S or (NIT^S to a fresh sample. 

Reaction. 2FeCl 3 +6NH 4 OH+3H 2 S = Fe 2 S 3 (brown black)-f-6NH 4 Cl 

+ 6H 2 0. 

Note.— If NH 4 OH is added to test (a) above, the reaction is the same a 
in (6) Experiment under ferrous salts, since FeCl 3 is reduced by H 2 S t< 
FeCl 2 , as follows: 2FeCl3+H2S = 2FeCl 2 +2HCl+S. 

Tests with Reagents Used for Confirming Iron 

27. Add potassium ferrocyanide to a portion of ferric solu 
tion. The precipitate is Prussian blue. For best results th< 
solution should be neutral or at most only slightly acid. Delicacj 




13 3 


THE METALS 


101 


)f test is 0.0000002 gram Fe in 100 cc. of solution. The color is 
aint green in very dilute solution, blue if the solution is more 
Concentrated. With increased concentration a precipitate forms. 
3ee list of ferric salts. 

Reaction.—4FeCl 3 +3K 4 Fe(CN) 6 = i Fe 4 [Fe(CN) 6 ] 3 , blueppt.+12KCl. 

Note .—Potassium ferricyanide gives a brown coloration, but no pre- 
lipitate with ferric iron solution. (A blue precipitate forms with ferrous.) 

28. Potassium thiocyanate, KCNS, gives a deep red precipitate 
3 r red or pink-colored solution according to the concentration of 
Ton. (Distinction from ferrous salts.) The reaction is reversible. 
jAn excess of the reagent increases the delicacy of the test— 
( ).00000007 gram Fe in 100 cc. of solution. 

Note .—KCNS also produces a color with HN0 3 . This acid, therefore, 
should be absent in the test sample. 

29. Reduction of Ferric Salts.—This is commonly accom¬ 
plished in the laboratory by H (Zn+HCl), H 2 S, SnCl 2 , SO 2 . 

(a) Reduce FeCl 3 solution strongly acid with HC1, by adding 
SnCl 2 . The reduction takes place quickly in hot solution, 
t (6) Reduce FeCh solution by passing in H 2 S into the acid 
solution. 

What color change takes place due to reduction? Write out 
reactions for (a) and (6). 

Note .—SnCU is used for the quantitative determination of iron. 


COBALT, Co++, Co+ + + 

In the general scheme of separations cobalt is found in the 
filtrate of the H 2 S group as cobalt chloride. For the following 
tests a solution of Co(N0 3 )2 or C 0 CI 2 may be used. 

30. To a solution of cobalt salt add NH 4 OH and then an 
ii* excess of NH 4 CI. 

ie Note —The blue basic salt dissolves in an excess of NH 4 OH or NH 4 C1, 



102 


QUALITATIVE ANALYSIS 


forming a brown-colored solution, which changes in the air or on boilin 
to a red or pink-colored solution. 

Reactions.—(a) CoC 1 2 +NH 4 OH = | Co (OH) Cl (blue) + NH 4 C1. 


(6) Co(OH)C 1+NH 4 OH = | Co (OH) 2 (pink)+NH 4 Cl. 

(c) Co (OH) 2 +2NH 4 C1 -f 2NH 3 = Co (NH 3 ) 4 C1 2 +2H 2 0. 

Note .—Presence of organic matter prevents precipitation of cobalt hydrox 
ide as well as the presence of NH 4 salts. 

31. To the solution obtained in Experiment 30 above add H 2 £ 
or (NH 4 ) 2 S. A black-colored precipitate is obtained, insolubL 
in excess (NEU^S. (NiS tends to dissolve. See Experiment 446 
under Nickel.) 


Reaction.— 

Co(NH 3 ) 4 Cl2+(NH 4 )2S+4H 2 0= ICoS (black)+2NH 4 C1+4NH 4 0H. 

Write out reaction with H 2 S. 

32. Dilute HC1 (sp.gr. 1.035) does not dissolve CoS. Aqm 
regia, however, dissolves the sulphide. Try this. 

Reaction.—3 CoS+ 8HN0 3 = 3Co(N0 3 ) 2 + 1 3S+ T 2N0+4H 2 0. 


33. Neutralize the solution with NaOH after expelling mosi 
of the acid by heating. A precipitate forms insoluble in excess, 

Reactions.—(a) CoCh+NaOH = | Co(OH)Cl (blue)+NaCl. 

(6) Co(OH)Cl+NaOH= J, Co(OH) 2 (pink)-fNaCl. 

Note .—Co (OH) 2 is soluble in NH 4 salts. Exposure to air gives the 
black Co(OH) 3 distinction from Ni(OH) 2 , which does not oxidize with air. 


34. To the alkaline mixture of cobalt salt add KCN solution 
in excess and Br water, warm, Co(CN) 2 light-brown precipitate 
dissolves in the excess of KCN. 


Reaction.—Co(CN) 2 +4KCN = K 4 Co(CN)g, brown. 





THE METALS 


103 


35. On warming in presence of an oxidizing agent a bright 
fellow colored solution is obtained. 

Reaction.—2K 4 Co (CN)«+H 2 0+O = 2 K 3 Co (CN)«+ 2 KOH. 

Note. —Nickel under the above conditions forms the black precipitate 
Ni(OH) 3 , hence a separation from nickel may be affected by this procedure., 

Confirmatory Tests for Cobalt 

36. Potassium Nitrite Test. —The reagent added in excess 
bo the concentrated cobalt solution, warmed, produces a yellow 
^crystalline precipitate K 3 Co(N0 2 )6. Addition of a saturated 
s solution of potassium salt (KC1) decreases the solubility of 

“K 3 Co(N0 2 ) 6 . 

r 

Note. —Nickel produces no precipitate with KN0 2 . 

37. Borax Bead Test. —A cobalt salt fused with borax gives a 
blue-colored bead. Try this. 

38. a-Nitroso-/3-Naphthol Test. —CioHe(NO)OH dissolved in 
50 per cent acetic acid gives a red precipitate, [CioH6(NO)0] 3 Co 
when added to a cobalt salt. The presence of free HC1 does not 
interfere. (Nickel in presence of HC1 gives no precipitate.) See 
page 112. 

MANGANESE, Mn+ + 

In the usual procedure of separation of the groups manganese 
is found in the filtrate of the H 2 S group in the divalent form. 
The salts of the oxide MnO and the acids are pink in solution or 
in crystallized form and colorless as anhydrides. 

Use a solution of MnSC >4 or MnCl 2 or Mn(N0 3 ) 2 . 

39. To a portion of the solution add NH 4 OH and note colors 
of the precipitate formed. Test the solubility in NH 4 CI solution. 

Reactions.—MnCl 2 + 2 NH 4 OH = 1 Mn(OH ) 2 (white)+2NH 4 C1. 

Mn(OH) 2 -fO (air) = [ Mn0 2 -H 2 0 (brown). 

Note. —NH 4 CI prevents precipitation only for a short time, as oxidation 




104 


QUALITATIVE ANALYSIS 


by air takes place and manganous acid, MnOa'IEO, is precipitated. Separa 
tion of Mn from Fe, A1 and Cr, by precipitation of these as hydroxides, i 
not complete in presence of considerable amount of manganese salt. 

The presence of organic matter interferes with the precipita 
tion of manganese. 

40. To the solution obtained in Experiment 39, add (NH^S o: 
pass in H 2 S gas. A pink-colored sulphide is obtained whicl 
darkens on exposure to the air (presence of Mn2C>3). 

MnCl 2 +2NH 4 OH -f H 2 S = MnS-f 2 NH 4 CI+ 2 H 2 O. 

Note. —Presence of NH 4 C1 assists precipitation of MnS, tartrates an< 
oxalates retard it. In boiling with large excess (NH 4 ) 2 S, the green hydratet 
sulphide is formed. 

41. Test the solubility of the precipitate in dilute HC1 (sp. gr 
1.035). 

Note. —The sulphide is also soluble in ace tie acid. Manganese may thu; 
be separated from NiS, CoS, ZnS. 

42. (a) To the solution obtained in Experiment 41, add NaOE'! 
and then Na 2 C >2 in excess. A dark-brown compound Mn02*H2C 
is formed. 

(6) Test the solubility of Mn02-H20 in hot dilute HNOj 
(sp.gr. 1.2). The dark-brown residue is Mn(> 2 . This affords 1 
method of separating Mn from Fe, since Fe(OH )3 dissolves ii 
HN0 3 . 

Confirmatory Tests for Manganese 

43. Lead Oxide Test.—(a) Place the precipitate obtained ir 
Experiment 42 (6) in a small beaker, add 10 cc. of strong HNOj 
(sp. gr. 1.42) heat to boiling and add 1-2 grams of red lead (Mn free) 
or Pb02. Allow to settle. The supernatant liquid will be 
colored violet red by the permanganic acid formed. 

Reaction.— 2 Mn 0 3 + 5 Pb 02 + 6 HN 03 = 2HMn0 4 (violet red) + l 2PbO 
+3Pb(N0 3 )2+2H 2 0. 





THE METALS 


105 


Note .—The presence of chloride interferes with the test. The precipitate, 
therefore, should be washed free of chloride. A trace of Mn may be detected 
by this procedure. Sodium bismuthate may be used in place of the lead oxide. 

( b ) Fuse a portion of the manganese precipitate on a platinum 
foil with a mixture of Na2C03 and KNO3 or KCIO3. Green 
r sodium manganate will be formed. 

1 MnS0.+2KN0 s +Na,C0 J = Na 2 S 04 +KN 0 ! +N 0 +C 0 2 +KMn 0 4) green. 

NICKEL, Ni++, Ni+++ 

j In the general scheme of separation nickel is found in this 
group as NiCb. Use a solution of Ni(NOs)2 or NiC^. 

44. (a) To a solution of nickel salt add NH 4 OH. 

Reaction—NiCl 2 +2NH 4 OH = j Ni(OH) 2 (green gelatinous) +2NH 4 C1. 

( 6 ) Does a precipitate form when NH4CI is added? 

Reaction—Ni(OH) 2 +2NH 4 Cl +2NH 3 = Ni(NH 3 ) 4 Cl 2 (blue-colored solu¬ 
tion) -J-2H 2 0. 

Note. —Organic matter prevents pecipitation of Ni(OH) 2 as well as the 
presence of NH 4 salts. 

45. To the solution of nickel salt containing NH 4 OH and 
NH4CI (Experiment 44 ( 6 )) add H 2 S gas or a solution of (NH^S. 

Reaction.—Ni(NH 3 ) 4 Cl 2 +H 2 S-{-2H 2 0 = | NiS (black) -f-2NH 4 Cl 
+ 2 NH 4 OH. 

Write out the reaction with Ni(NH3)4Cl2+(NH4)2S. 

Notes. —If the solution contains a large excess of (NH 4 ) 2 S in presence of 
free NH 4 OH, the filtrate from NiS will be colored brown by dissolved Ni. 
From this solution NiS may be completely precipitated by boiling in presence 
of sufficient acetic acid to neutralize free NH 4 OH. No precipitate forms in 
presence of much free acetic acid, but the addition of NaC 2 H 3 0 2 causes 
precipitation. The presence of large quantities of NH 4 salts prevents the 
dissolving of NiS. 

NiS oxidizes in the air, forming water-soluble NiS0 4 . This is avoided by 
quick filtration and presence of H 2 S in the wash water. 




106 


QUALITATIVE ANALYSIS 


46. Test the solubility of NiS in dilute HC1 (sp.gr. 1.035). 

Note .—The sulphide is insoluble in dilute HC1 but dissolves in aqua regia. 

Reaction.— 3NiS+2IIN0 3 +6HCl = 3NiCl 2 -f | 3S+ T 2N0+4H 2 0. 

The sulphur is oxidized by HN0 3 , forming H 2 S0 4 with libera¬ 
tion of NO gas. Write out reaction. 

47. (a) Dissolve the sulphide NiS in aqua regia. Neutralize 
with NaOH and add an excess. Now oxidize the nickelous salt 
with bromine water. 

Reaction.— Ni(OH) 2 +NaOH+Br = J. Ni(OH) 3 +NaBr. 

Note. NaOH or KOH precipitate Ni(OH) 2 insoluble in excess. The 
precipitate does not oxidize in the air as does Co(OH) 2 . 

(6) In place of the excess of NaOH add KCN to the slightly 
alkaline solution. The green precipitate is Ni(CN) 2 ; with an 
excess, of KCN the precipitate dissolves forming K 2 Ni(CN) 4 . 
Heat this solution with Br water as in Experiment (a) above. 
The black precipitate is Ni(OH) 3 . 

Note. Cobalt does not precipitate under similar treatment, hence it 
may be separated from nickel by this procedure. 

Confirmatory Tests for Nickel 

48. Borax Bead Test.—The borax bead is colored brown by the 
NiS. Test a mixture of CoS and NiS with a borax bead. Note 
that the blue color predominates. What inference do you draw 
from this last, test? 

49. Dimethyl-glyoxime Test.—Add a 1 per cent alcoholic solu¬ 
tion to an ammoniacal solution of nickel salt. A red-colored pre¬ 
cipitate is obtained. In an extremely dilute solution a pink color 
is seen. Delicacy in 100 cc. of solution 0.00000025 g. Ni may be 
detected. 

Reaction.—2(CH 3 ).aN 2 0 2 H 2 +NiCl 2 +2NH 4 0H 

=2NH 4 C1+[ (CH 3 ) 2 C 2 N 2 0 2 H] a N i +2H 2 0. 




THE METALS 


107 


ZINC, Zn+ + 

Zinc is in the form of chloride, in the general procedure of 
analysis, in the filtrate from the H 2 S group. 

Use a solution of ZnSC>4 or ZnCU- 

50. Ascertain the following facts: Does a precipitate form 
upon the addition of NH4OH? If so, note its color and ascertain 
whether it dissolves upon the addition of an excess of the reagent. 
Does the precipitate dissolve upon the addition of NH4CI? Does 
heating the solution cause a coagulation of the precipitate? 

Reactions.—ZnCl 2 +2NH 4 OH = | Zn(OH) 2 +2NH 4 Cl. 

Zn (OH) 2 +2NH 4 C1+2NH 3 = Zn(NH 3 ) 4 Cl 2 +2H 2 0. 

51. To the solution made alkaline with NH4OH+NH4CI 
add a few cc. of (NHO 2 S or pass in H 2 S gas. Note the color of 
the precipitate. Filter. 

Reaction.—Zn(NH 3 ) 4 Cl 2 +(NH 4 ) 2 S+4H 2 0 = ZnS (white) +2NH 4 C1 
+4NH 4 OH. 

52. Remove a portion of the precipitate with a spatula and 
place in a porcelain dish. Pour over it about 20 cc. of cold 
2N-HC1 (1.035), stir, and note whether the precipitate dissolves. 

Reaction.—ZnS+2HCl ^ ZnCl 2 + T H 2 S. 

Note. —ZnS, although readily soluble in mineral acids, does not dissolve 
easily in acetic acid, and may be precipitated in presence of free acetic acid 
from its solutions by H 2 S. 

53 . If solution is effected, evaporate to half its bulk, cool, 
and make alkaline with NaOH solution. Now add Na 2 0 2 in 
small portions until about 2 grams has been added. Does pre¬ 
cipitation take place? Heat to decompose the peroxide until 
effervescence ceases. If precipitation has taken place, note 
color of substance; if not, note whether the solution is colored. 

Reactions.—(a) ZnCl 2 +2NaOH = f Zn(OH) 2 -f2NaCland 

(b) Zn(OH) 2 +2NaOH*=>Na 2 Zn0 2 (sol.) +2H 2 0. 



108 


QUALITATIVE ANALYSIS 


Note .—Boiling the solution of sodium zincate causes the precipitation o 
Zn(OH) 2 . Reaction ( b ) therefore, is reversible. A large excess of NaOi 
prevents this precipitation. 

54. Acidify the solution with HNO3 (1-42) and then mak( 
alkaline with NH4OH. Does a precipitate form? 

55. Acdify with 30 per cent acetic acid solution, avoiding ar 
excess, add a little NaC 2 Hs 02 and heat nearly to boiling, pass in 
H 2 S gas to saturation. A white precipitate is Zn . 

56. Confirmation of Zinc.—While the solution is still hot filter ofl 
the ZnS precipitate on a filter and dissolve by pouring repeatedly 
over it 5-10 cc. HNO 3 (1.07). To the filtrate add 4-5 drops of 
N/100 Co(N 0 3 )2; evaporate almost to dryness to expel the acid; 1 
then neutralize with Na 2 C 03 (10 per cent), adding § cc. in excess.! 
Evaporate to dryness and ignite gently until the purple color 
of the cobalt disappears. Allow to cool. A green color is due 
to a compound of zinc and cobalt oxides, probably cobalt zincate, 
CoZnC> 2 . 

Notes .—The cobalt nitrate test may be made on any dry zinc compound 
by moistening with cobalt nitrate and igniting the mixture. 

ZnS may be precipitated by H 2 S from a solution of Na 2 Zn0 2 , in presence 
of NaOH. 

Table of Reactions 

The student is advised to make a study of the comparative reactions 
of the ammonium sulphide group by referring to the Tables in Part V. The 
tests may be conducted in the laboratory if desired. 




THE METALS 


109 


3 Outline of Separations of the Ammonium Sulphide Group 
(Iron and Zinc Groups) 

:e Three general procedures are considered in the order of their 
nerit for separation and detection of the members of this group. 

D (a) From the chemical reactions it is evident that ammonium 
n sulphide will precipitate all the metals of this group after making 
die solution alkaline with ammonia. The group is thus separated 
From the alkaline earths and the alkalies, and the members then 
isolated by the procedure described later. This method is con- 
f ddered the most reliable of the three, as it does not possess objec¬ 
tions of the optional methods ( b ) and (c). 

( b ) If ammonia is added to a solution containing all the 
• metals of the group in presence of sufficient ammonium chloride, 

! the trivalent metals iron (ferric), chromium and aluminum are 

precipitated as hydroxides, while the remaining elements are in 
solution. The group is thereby divided into two sub-groups, thus 
simplifying subsequent separations. The objection to this pro¬ 
cedure is the fact that manganese and zinc, if present in small 
amounts, may be occluded and carried out of solution by the 
hydroxides of the trivalent elements and thus escape detection. 
By dissolving and reprecipitating these hydroxides this difficulty 
is largely overcome. 

(c) The third procedure is given on account of its application 
in gravimetric methods to determining manganese and zinc. 
A knowledge of this procedure is considered advisable in this 
preliminary course. This basic acetate precipitation of the 
trivalent elements occurs when sodium acetate is added in suffi¬ 
cient excess to nearly neutral solutions of ferric iron, aluminum 
and chromium and the solution diluted to a comparatively large 
volume and boiled. As in case of the ammonium hydroxide 
method the group is divided into two and each subgroup then 
treated by suitable procedures. The objection to this procedure 
is the fact that chromium is incompletely precipitated if it is 
present in relatively large amounts with small amounts of iron 





110 


QUALITATIVE ANALYSIS 


and aluminum. Under this condition the precipitation of al 
three elements is incomplete. With iron and aluminum in pre 
dominance the method is satisfactory. I 

In the first procedure, which we may designate as the sulphid< 
method, the precipitate consists of the hydroxides of aluminuirj 
and chromium and the sulphides of iron, cobalt, nickel, man-* 
ganese and zinc. Cobalt and nickel sulphides are insoluble ir. 
cold dilute HC1 (sp.gr. 1.035). «i 

The hydroxides of aluminum and chromium and the sulphides ta 
of the remaining elements dissolve, and pass into the filtrate when 
the mixture is treated with cold dilute HC1 and transferred to a j! 
filter. The residue NiS and CoS is brought into solution with ‘ 
aqua regia and nickel and cobalt determined by means of the \ 
borax bead and the wet methods given in the tabulated procedure. 
The main filtrate contains the chlorides of Al, Cr, Fe, Mn and Zn, 
and an excess of HC1 with H 2 S. The greater part of HC1 and 
all the H 2 S are expelled by evaporation and the solution then 
made strongly alkaline by addition of Na 2 C> 2 . The oxidation 
converts chromic chloride into soluble sodium chromate, the 
alkali forms the water-soluble aluminate and zincate, while iron 
and aluminum are precipitated as hydroxides. 

By filtration, a separation of Fe(OH ) 3 and MnC^H^O from 
the solution containing Al, Cr and Zn is effected. Manganese 
and iron may be readily identified in the residue in presence of 
each other; or by separation, when a rough estimation of the 
quantity is desired. Chromium may be recognized by the yellow 
color its solution as a chromate imparts to the filtrate from iron 
and manganese. Aluminum may be precipitated from the 
solution by neutralizing the alkali with HN0 3 and precipitating 
with NH4OH in presence of NH 4 CI, which prevents precipitation 
of Zn(OH) 2 , while chromium as chromate does not precipitate. 
By making the filtrate from Al(OH ) 3 acid with acetic acid and 
adding BaCl 2 solution chromium is precipitated as yellow BaCr(> 4 . 
Zinc may now be determined in the filtrate by precipitating as 
white ZnS by H 2 S. 





THE METALS 


111 


Separation of Ammonium Sulphate Group—Sulphide Method 

\l 


(a) li the solution is the filtrate of the H 2 S Group, boil it to expel sul- 
phureted hydrogen, e.g., until no odor of the gas remains, then add 1-2 cc. 
)f cone. HN0 3 (1.42), and boil to oxidize the iron. 

( b ) If oxalates or tartrates are present, destroy by ignition. (See Notes.) 

(c) If phosphates are present, they should be removed. About one-tenth 
3 f the solution should be used to detect these interfering substances, unless 
known to be absent, before proceeding with the analysis. (See Notes.) 

(d) To the hot solution, free from phosphoric acid, etc., add NH 4 C1, 1 :4 
(unless already present or the solution contains considerable HC1), then add 
NH4OH until the odor of ammonia is distinct upon shaking solution. If 
precipitates form, Al, Fe, and Cr may be present. Observe the color of the 
hydroxides. Reddish brown is Fe (OH) 3 ; white may be Al (OH) 3 ; and grayish 
green or lavender, Cr(OH) 3 . Now add (NH 4 ) 2 S slowly, or pass in H 2 S, if Ni 
is suspected, until the solution is saturated. Vapor arising from the flask will 
then blacken a filter paper moistened with lead acetate. Coagulate the 
precipitate by heating and shaking. Filter immediately and wash the precipi¬ 
tate with 1 per cent solution of (NH 4 ) 2 S and then with distilled water, keep¬ 
ing the funnel covered between intervals with a watch glass to prevent oxida¬ 
tion by the air. 

II. 


Precipitate.—White Al(OH) 3 ; green 
Cr(OH) 3 ; white ZnS; pink MnS; black 
FeS; black NiS; black CoS. 

Tear off the portion of the filter con¬ 
taining the precipitate and drop into a 

small Erlenmeyer flask. Pour over the__ 

sulphides, etc., 25 to 50 cc. of cold 

2N-HC1 (1.035) (1 vol. HC1 (1.20) to 6 vols. H 2 0). Cork the flask and shake 
to facilitate solution of soluble sulphides. After 4-5 minutes filter and wash 
the residue immediately with wash water containing H 2 S and NH 4 C1. 


Filtrate.—The metals of the 
(NH 4 ) 2 C0 3 and the Soluble Group 
if present will be found here, phos¬ 
phoric acid being absent. Reject 
if these groups are not to be ex¬ 
amined. (See page 134.) 










112 


QUALITATIVE ANALYSIS 


III. 


Residue.—Black NiS, black CoS. 
(If light colored, dissolve in warm HC1 
and add to filtrate.) Test the residue 
with the borax bead. Blue indicates 
Co. Ni may be present. Yellow or 
brown indicates Ni. Co may be 
present in very small amount. In 
case the bead is blue, tear off the por¬ 
tion of the filter containing ppts. 
Place in a casserole and add 5-15 cc. 
HC1 ( 1 . 12 ) and several drops of HN0 3 
(1.42). Warm until the black ppt. 


Filtrate.—Fe+ ++ ;Mn + + ; Cr+ + + 
Al + + + ; Zn + + ; Cl“" ions. Evaporat 
to half its bulk to remove a portion c 
the acid and to expel H 2 S. Cool, an< 
make alkaline with C.P. NaOH solu 
tion. Add 1-3 grams of Na 2 0 2 in smal 
portions. The solution should nov 
be strongly alkaline. Heat until effer 
vescence ceases. Filter. Wash th< 
precipitate with warm water. Analyze 
precipitate according to method I\ 
and filtrate by method VI. 


dissolves and filter. Evaporate almost' 
to dryness, then add 5 cc. water and NaOH, drop by drop, until the solution 


is neutral or a trace of precipitate forms. 


III. Divide into two portions, A and B. 


A. Use either of the following tests. 

1. Add 15 cc. 30 per cent sol. 
HC 2 H 3 0 2 and then 50 cc. 30 per cent 
sol. KN0 2 . Dilute to 100 cc. and 
allow to stand some time. A fine yel¬ 
low precipitate is K 3 Co(N0 2 ) 6 . 

Confirm.—Filter, wash with KN0 2 
sol. Test residue with borax bead. 
Blue indicates cobalt. If ppt. is small, 
burn filter and test the ash. 

2. Make the solution faintly acid 
with a few drops of dilute H 2 SO 4 and 
evaporate to dryness to expel HNO 3 , 
neutralize with NH 4 OH and add an 
equal volume of glacial acetic acid 
followed by an excess of a 50 per cent 
acetic solution of a-nitroso-/3-naphthol. 
A brick-red precipitate proves the 
presence of cobalt. The precipitate, 
tested with borax in the flame, gives 
a blue-colored bead. 


B. Use either of the following 
methods. 

1. Make the solution slightly acid 
with HC1, then neutralize with am¬ 
monia and add a sufficient excess to 
give a decided ammoniacal odor to the 
sample. Now add an excess of 1 per 
cent alcoholic solution of dimethyl 
glyoxime. A scarlet or pink-colored 
precipitate, Ni[(CH 3 ) 2 C 2 N 2 0 2 H] 2 , 
proves the presence of nickel. 

2. Add 10 per cent sol. KCN drop 
by drop until any precipitate, that 
forms, redissolves, then 2 cc. in excess. 
Heat to 50°-60° for 5 min., stirring 
frequently. Filter into a test tube. 
Add fresh cone. NaBrO until filter 
paper moistened in sol. of KI and 
starch is colored blue or brown. For¬ 
mation of a dark ppt. indicates Ni. 
Borax bead test=brown bead. 








THE METALS 


113 


V. Precipitate from Na 2 C >2 treatment under Filtrate III. 


Precipitate.—Brownishred F e (OH) 3 ; 
ark brown Mn0 2 • H 2 0. 

(o) For detection of Mn and Fe 
ise either (a) or ( b ) methods. 

(а) Washppt. 

Test for Mn.—Take up small 
.mount of ppt. on a Na 2 CC>3 bead, 
CC10 3 , a bluish green or green mass 

Test for Fe.—Dissolve ppt. in HC1. 
irm with K 4 Fe(CN) 6 test = blue ppt. 

(б) Remove precipitate from filter 
with 20-30 cc. dilute HN0 3 

h with a little warm water. 


Filtrate.—Light yellow Na 2 Cr0 4 ; 
colorless NasAlCh; Na 2 Zn0 2 . Pro¬ 
ceed to the analysis of the Aluminum 
Subgroup under VI. 


heat and dip hot bead into powdered 
is due to NaMn0 4 . 

A yellow color indicates FeCl 3 . Con- 

paper and place in a casserole and 
(1.20), heat to boiling, stir, filter, and 


V. _ 

Residue.—Dark brown or black 
Mn0 2 . 

Confirm by adding to the pre¬ 
cipitate in a test tube 1-2 grams of 
red lead (Mn free) and 10 cc. of 
HN0 3 (1.42). Boil 2-3 minutes, and 
allow to settle. The supernatant 
liquid will be colored violet-red by the 
permanganic acid formed. ^ 


Filtrate.—Fe(N0 3 ) 3 . 

Make strongly alkaline with 
NH 4 OH and heat to boiling to coagu¬ 
late the precipitate. A brownish red 
precipitate indicates Fe(OH) 3 . 

Confirm by dissolving precipitate 
by adding warm dilute HC1 to washed 
residue. Add a few drops of the fil¬ 
trate to 5 cc. KCNS. A deep-red 
color is due to the feebly ionized salt 
Fe(CNS) 3 , proving the presence of 
iron. 


VI. Filtrate from Na 2 C >2 treatment under Filtrate III. _ 

Acidify the filtrate, containing Al, Cr, and Zn, with HN0 3 (1.42) add 2-3 
grams of NH 4 C1 and then make slightly alkaline by the addition of NH 4 OH 
(0.96) and about 2 cc. in excess. (End points can be determined by placing 
a drop of the stirred solution on litmus paper.) Coagulate by heating almost 
to boiling. Filter and wash the precipitate with hot water. 











114 


QUALITATIVE ANALYSIS 


VII. 


Precipitate.—May be white, gelatinous 
Al(OH)?. If silica is suspected dissolve the pre¬ 
cipitate in 5 cc. of HNOs (1.20). (Use only a 
portion if the precipitate is large.) Add 4-5 
drops of N/100 cobalt nitrate, Co(N0 3 ) 2 . 

Evaporate the solution to dryness, then add 
a drop or so of water, and soak up the liquid 
on a small piece of filter paper. Roll up the 
paper and ignite in a flame, holding the paper 
in the spiral of a platinum wire. Drop the ash 
in a crucible and heat to destroy the carbon. A 
blue residue in the ash is due to an aluminum 
cobalt compound. 



Filtrate.—Cr, Zn, etc. 

Acidify with 30 per cen 
solution of acetic acid, avoid | 
ing over 2 cc. in excess. I 
the solution is colorless i 
chromium is absent. In this 
case proceed immediately tc 
the analysis of zinc. Ir 
case the solution is colorec 


slightly yellow, add about 10 cc. of 10 per cent solution of BaCl 2 , and allow 


to stand 5-10 min. and filter. 
VIII 


Precipitate.—Yellow 
BaCrC>4. 

Confirmation of chromium 
may be made as follows: 
Filter and dissolve the pre¬ 
cipitate by pouring repeat¬ 
edly over it 5-10 cc. HN0 3 
(1.07). To the cold filtrate 
in a test tube add about 2 
cc. of ether and 1 cc. of a 3 
per cent solution of H 2 0 2 . 
Shake well and settle. A 
blue color is imparted to the 
ether layer, probably due to 
the formation of HC 1 O 4 , 
perchromic acid. 


Filtrate.—May contain Zn. 

Pour into an Erlenmeyer flask. Warm to 
50°-60° and saturate with H 2 S. Cork and allow 
to stand 5-10 minutes. A white flocculent pre¬ 
cipitate is ZnS. In case of doubt confirm zinc 
by Co (NO 3 ) 2 test, given in the Preliminary 
Reactions in Experiment 56 on page 108. 

Confirmation of Zinc.—Transfer the precipi¬ 
tate to a filter and dissolve it by pouring repeat¬ 
edly over it 5-10 cc. HN0 3 (1.07). To the 
filtrate add 4-5 drops of N/100 Co (NO ) 2 ; 
evaporate almost to dryness to expel the acid; 
then neutralize with Na 2 C0 3 (10 per cent sol.), 
adding \ cc. in excess. Evaporate to dryness 
and ignite gently until the purple color of the 
cobalt disappears. Allow to cool. A green color 
is due to the presence of a double oxide of zinc 
and cobalt. 













THE METALS 


115 


Notes on the Analysis of the Ammonium Sulphide Group 

. 

Procedure A 

Interfering Substances.—The oxalates and phosphates of the heavy metals 
re insoluble in neutral or alkaline solutions or in solutions containing weak 
cids such as acetic acid. Upon making the solution alkaline with NH 4 OH 
)r precipitation of (NH 4 ) 2 S Group, if oxalic acid and phosphoric acid are 
resent, Ca, Ba, Sr, and Mg will be precipitated as phosphates or oxalates, 
ence the removal of the acids is necessary. Since these salts are insoluble 
1 neutral or alkaline solutions, the acid radicals need not be looked for in 
Dlutions of salts that are readily soluble in hot water. Oxalates and tar- 
rates rarely occur in actual analysis of inorganic substances, so that a test 
3 r these is not generally made. If present, they may be removed by evaporat- 
ng the solution to dryness and igniting with ammonium nitrate. Organic 
ompounds may also entirely prevent the precipitation of the Iron Group, 
rhese substances are generally detected and removed in the preparation of 
he solution. 

Test for Oxalate.—Add, drop by drop, 5-10 cc. of a hot solution of Na 2 C0 3 
10 per cent) to a small portion of the H 2 S filtrate. Shake to mix well, and 
How to stand for several minutes; filter if necessary. Then add a few cc. 
>f CaCl 2 solution. A white precipitate indicates the oxalate CaC 2 0 4 . 

Test for Phosphate.—Strongly acidify a small portion of the solution with 
1N0 3 (1.42), and pour it into four times its volume of ammonium molybdate 
olution. Warm to 60° or 70° for about 10 to 30 minutes. A fine yellow 
>recipitate indicates the presence of a phosphate. 

Removal of Phosphoric Acid.—The following reaction of phosphoric acid 
akes place with heavy metals in alkaline solutions: 

(NH 4 ) 2 S Group—H 3 PO 4 +FeCl 3 -(-3NH 4 OH = FePO 4 +3H 2 0+3NH 4 C1. 

(NH 4 ) 2 C0 3 Group—2H 3 P0 4 +3BaCl 2 +6NH 4 0H = 

Ba 3 (PO 4 ) 2 +6H 2 0+6NH 4 C1. 

If phosphates are present, the acid radical should be removed as follows: 

Test one-tenth of the solution for iron by making alkaline with NH 4 OH 
,o precipitate the iron, then dissolving the precipitate in HC1 and adding a 
ew drops of the filtrate to about 5 cc. of KCNS. A blood-red solution 
Droves iron to be present. 

To the remainder of the solution add NH 4 OH until barely neutral. (A 
slight precipitate will form, which remains insoluble on shaking.) Now add 
icetic acid to acidity and about 5 cc. of ammonium acetate (50 per cent 




116 


QUALITATIVE ANALYSIS 


solution). If the precipitate is not brownish red in color, add, drop by dro 
FeCl 3 until the red color is produced. Unless the iron is in excess, the pr 
cipitate of FeP0 4 will be yellowish white. To insure complete removal 
the phosphoric acid an excess is added, but care should be taken not to add t< 
much, as ferric phosphate is soluble in FeCl 3 . Add water until the volume 
100 cc. and boil for 5 minutes in a 250 cc. flask. (Add more water if tl 
precipitate is large.) Allow to settle and filter while hot. To the filtral 
add 2 to 5 cc. more of the ammonium acetate to precipitate excess of ire 
as basic ferric acetate. Boil and filter if a precipitate forms. 


Filtrate contains salts of (NH^S and 
(NH 4 ) 2 C0 3 Groups, e.g., Co; Ni; Zn; Mn; 
Al; Cr; Ca; Ba; Sr; Mg. 

Pass in H 2 S upon addition of NH 4 OH and 
NH 4 C1. 


Precipitate contains bas 
acetate, hydroxide, and pho; 
phate of iron. Reject. 


Precipitate sulphides of 
(NH 4 ) 2 Group. Analyze 
in usual way. 


Filtrate contains the salts of the (NH 4 ) 2 CC 
Group with magnesium. Use for the analysis c 
these elements. 


Reaction of iron on phosphoric acid in presence of ammonium acetate.— 
FeCl 3 +H 3 PO 4 +3NH 4 C 2 H 3 0 2 = FePO 4 -f-3NH 4 C1+3HC 2 H 3 0 2 . Ammoniur 
acetate prevents formation of free HC1 which would dissolve FeP0 4 ; e.g. 
FeCl 3 +H 3 P0 4 = FePO 4 +3HC1. 

Analysis.—Regarding the separation of the members of this group, severa 
methods are in use. The Sulphide and the Hydroxy-Sulphide methods her< 
given are more generally used. The author gives precedence to the firsl 
method, which in his opinion gives more reliable results. Although the seconc 
method has the advantage of simplicity, yet difficulties are apt to arise under 
certain circumstances. For example, manganese may precipitate with iron 
aluminum and chromium upon oxidation. Zinc may also be carried dowr 
in the presence of an excess of chromium. Likewise, traces of Ni and Cc 
may be lost, due to the hydroxides carrying down the elements, when Fe, Al, 
or Cr are present in large amounts. 

I. Precipitation. The removal of the H 2 S is necessary for the observation 
of the precipitation of certain members of the group that are thrown down as 
hydroxides by ammonium hydroxide in the presence of NH 4 C1. Iron is 











THE METALS 


117 


precipitated as grayish white, Fe(0H)2, changing to green and finally to 
brownish red, Fe(OH) 3 . Chromium precipitates as grayish green, Cr(OH) 3 ; 
aluminum as white, Al(OH) 3 . (In large quantities zinc precipitates as white, 
Zn(OH) 2 ; manganese as brown, Mn(OH) 2 ; cobalt as rose-red, Co(OH) 2 , 
changing to brown.) (The rare elements may be found here, as white, 
Be(OH) 6 ; white gelatinous, Th(OH) 4 ; white flocculent, Zr(OH) 4 ; white, 
Ce 2 (OH) 6 ; white, La 2 (OH) 6 ; pale rose, Di 2 (OH) 6 ; white, Y 2 (OH) 6 ; white, 
Yb 2 (OH) 0 ; white, Se 2 (OH) e ; white, Er 2 (OH) 6 ; white, H 2 Ti0 3 ; white, 
Ta0 2 -0H; white, H 3 Nb0 4 ; yellow, (NH 4 ) 2 U 2 0 7 .) 

The monosulphide of ammonia is used in place of the polysulphide, as the 
latter dissolves NiS and adds sulphur to the precipitate, coloring the filtrate 
yellow. H 2 S is used in place of (NH 4 ) 2 S when nickel is present, as the sulphide 
of nickel dissolves slightly in the latter and scarcely at all in the gas. 

If HC1 is present in the solution, NH 4 C1 is formed. If not, this reagent 
should be added, as it prevents the precipitation of Mg(OH) 2 and renders 
Al(OH) 3 less soluble. 

A small amount of precipitate is apt to escape notice, owing to its trans¬ 
parency in case of light-colored precipitates, hence care should be used before 


pronouncing the group absent. 

Ammonium sulphide precipitates white, ZnS; pink, MnS, oxidizing to 
brown, Mn.Oj; black, CoS; black, NiS; it changes the hydroxide of iron to 
black, FeS, but produces no change on the hydroxides of aluminum or 

chromium. _ . , , 

(The sulphides of the rare elements, T1 2 S and U0 2 S, are dark brown. 

Ti, Be, Zr, remain as hydroxides.) 

The sulphide of nickel may dissolve slightly, coloring the filtrate yellowish 
brown This may be prevented by avoiding an excess of NH 4 OH and by 
precipitating the sulphides by H 2 S or by (NH 4 ) 2 S in a small Erlenmeyer 
flask, keeping the flask corked during intervals to prevent action of the air 
and by filtering rapidly, keeping the filter funnel covered by a watch glass 
between intervals of washing. NH 4 C1 prevents formation of soluble colloidal 
solutions, and H 2 S prevents oxidation. Hence these should be added to the 
wash water. If the filtrate is brown, make barely acid with acetic acid, boil 

and filter. , ■ . . . . e 

II. The separation of nickel and cobalt from the remaining elements of 
the group depends upon the comparative insolubility of NiS and CoS in cold 
2N-HC1, while the remaining precipitates dissolve. The corked flask is 
used as a precaution against the formation of sulphates by the oxidizing 

action of the air. , u , _ 

III. The borax bead tests may be conclusive for nickel or cobalt when 

existing alone, but if both are present, the intense blue of the cobalt compound 




118 


QUALITATIVE ANALYSIS 


masks the color of that of nickel so that a separation has to be made in order 
to detect the latter. 

A. K 3 Co(N0 2 )6, although slightly soluble in water, is difficultly soluble 
in a concentrated solution of potassium nitrite, hence use excess of that 
reagent. The precipitation takes place slowly. Nickel will precipitate 
only in concentrated solutions. 

B. KCN in neutral solution first precipitates green, Ni(CN) 2 ; and dark 
brown, Co(CN) 2 . These dissolve in an excess of KCN, forming the soluble 
salts K 2 Ni(CN) 4 and K 4 Co(CN) 6 . NaBrO decomposes KCN, forming 
KCNO, which then oxidizes nickel to the nickelic state, whereupon it is 
precipitated as brownish black, Ni(OH) 3 by the NaOH formed in the solution. 

Cobalt, although already in the cobaltic state, is not precipitated because 
its complex ion, Co(CN)" / 6, is not sufficiently ionized to react with NaOH 
to form the insoluble Co(OH) 3 , hence cobalt remains in solution. 

NaBrO is made by adding Br to a 10 per cent solution of NaOH until the 
solution is distinctly red and then adding half its volume of NaOH. As the 
reagent decomposes, it must be used fresh. NaOH and Br water may be 
used instead. The starch iodide test is used to show that an excess of the 
reagent has been added sufficient to destroy excess of KCN and to oxidize 
nickel to the nickelic state. 

In the final confirmation of nickel it must be remembered that the solu¬ 
tion must be saturated. The color will not appear until the solution is nearly 
saturated with hydrogen sulphide gas. 

In the precipitation of iron and manganese the peroxide is added in small 
portions at a time to a cold solution to prevent, as far as possible, its decom¬ 
position, which would take place with explosive violence from a hot solution. 
A steady evolution of oxygen shows that a sufficient quantity has been added. 
Chromium is oxidized to chromate, iron to Fe(OH) 3 , and manganese to Mn0 2 . 
The peroxide should be free from A1 and Si. 

IV. The insolubility of the manganese compound in nitric acid is taken 
advantage of in the separation of manganese from iron, Fe(OH) 3 being soluble. 

V. Cobalt and nickel may be precipitated with the manganese owing to 
their slight solubility in dilute HC1 and their reprecipitation by NaOH and 
Na 2 0 2 . Manganese when precipitated is first light colored, rapidly turning 
brown, due to oxidation. In case of doubt the confirmatory test may be made. 

2MnS0 4 +5Pb0 2 +6HN0 3 =2PbS0 4 +3Pb(N0 3 ) 2 +2H 2 0+2HMn0 4 , violet- 
red. 

Iron is recognized by its brownish red color as a hydroxide, manganese 
being a dark brown. The confirmation of iron is reliable if nitric acid is 
absent. The decomposition of KCNS by this reagent will cause a red 
color. 







THE METALS 


119 


VI. The solution contains aluminum, chromium, and zinc. Nitric acid 
is used in place of HC1 to prevent risk of reduction of chromic acid. 

The excess of NH 4 OH is added to keep the zinc in solution. A large excess 


would dissolve Al(OH) 3 . 

The reagents NaOH and Na 2 0 2 are apt to contain aluminum and silica as 
impurities. A blank test should be made to determine their purity. 

VII. The confirmation test for aluminum is made to guard against mistak¬ 
ing Si(OH) 2 0 for Al(OH) 3 . The former gelatinous substance does not dissolve 
in HNO 3 , whereas Al(OH ) 3 will go into solution. In the cobalt test for alumi¬ 
num the latter element must be in excess for a satisfactory result. A second 
confirmation test is made as follows: Dissolve the hydroxide in HC1 (1.12), 
and add \\ volumes of ether. Saturate the mixture with HC1 gas. A crystal¬ 


line, colorless precipitate is A1C1 3 -6H 2 0. 

The blue compound formed by the cobalt nitrate test is probably a double 
oxide of aluminum and cobalt, and may be Co(A10 2 ) 2 . An excess of cobalt 
would obscure the blue, owing to the formation of the black oxide of cobalt. 

VIII. A yellow-colored solution is generally an indication of the presence of 
chromium. In the confirmation test an excess of H 2 0 2 should be avoided, as 
it is apt to decompose the higher oxide of chromium, causing the test to fail. 

An immediate formation of a flocculent precipitate, upon the addition of 
H 2 S is a characteristic test for zinc. Only one other sulphide of the group 
is light colored, e.g. MnS, but this is soluble in acetic acid. 

Pb0 2 test fails if chloride is present in the manganese precipitate. 


120 


QUALITATIVE ANALYSIS 


The Hydroxide-Sulphide Method of Separation 1 
Optional Method B 


If the solution contains H 2 S it should be expelled by boiling. Now add 
2-3 cc. HNO 3 (1.20) and again boil. (Filter if sulphur separates.) Now 
add 2-3 cc. NH 4 C1 (if HC1 is not already present) and add a slight excess of 
NH 4 OH; boil and filter at once. 


Precipitate—Fe(OH) 3 , red; Cr(OH) 3 , green; Al(OH) 3 , 
white. Wash with hot water and dissolve in a few drops of 
HC1 (1.12). Transfer the cold solution to a casserole and 
add Na 2 0 2 in small quantities at a time until the mixture is 
strongly alkaline; boil to decompose excess of Na 2 0 2 , and 
filter. 


Solution.—Na 3 + A10 3 -and 

Na 2 + Cr0 4 . Acidify with acetic 
acid and divide into two portions. 


Filtrate.— 

Co++Cl 2 -; 
Ni++Cl 2 -; 
Mn++Cl 2 -; 
Zn++Cl 2 -; 
and may also con¬ 
tain the metals of 
the (NH 4 ) 2 C0 3 
and the Soluble 
Groups. Boil 
and pass in H 2 S 
through the hot 
solution until it 
smells strongly 
of the gas. Fil¬ 
ter and wash the 
precipitate with 
hot water con¬ 
taining a few 

. . . drops of (NH 4 ) 2 S. 

Wash the precipitate into a beaker with dilute HC1 (1.035) and allow to stand 
5-10 minutes. (If the precipitate is not black, Co and Ni are absent. If this 
is the case, dissolve the residue in HC1 (1.12), and proceed at once to the 
analysis for manganese and zinc.) 


Residue.—Fe(OH) 3 . 
Dissolve in warm HC1 
(1.12), and test for Fe 
with K 4 Fe(CN) G or 
KCNS. With first re¬ 
agent a blue coloration 
is due to Fe 4 (Fe(CN) 6 ) 3. 
A red ppt. with KCNS 
is Fe(CNS) 3 . 


(a) Add 
Pb(C 2 H 3 0 2 ) 2 . 

A yellow ppt. is 
PbCr0 4 . 

Confirm Cr by 
H 2 0 2 ether test. 


(b) Add 
NH 4 OH in 
slight excess and 
boil. A white, 
gelatinous pre¬ 
cipitate indi¬ 
cates aluminum. 

Confirm b y 
Co(N 0 3 ) 3 test. 


1 If chromium and zinc are both present, they are apt to precipitate each 
other in an ammoniacal solution. Manganese is also apt to precipitate when 
present in large amounts. In such case, separation of Al, Fe, and Cr as 
hydroxides is not satisfactory. 

















THE METALS 


121 




Residue may be CoS and NiS, black. 
Test for Co with borax bead; if present, 
the bead will be colored blue. If bead 
is brown, Ni is present. Since the blue 
color of the cobalt would mask the 
brown color of nickel, it is necessary to 
test for Ni. Positive tests for nickel 
and for cobalt may be found in the 
General Procedure A, Section III, page 
112 . 


Solution may contain Mn + + 
Cl 2 “, Zn+ + Cl 2 - (trace of Ni). 
Boil to expel H 2 S and add an excess 
of NaOH; boil and filter. 


Precipitate.— 

Mn(OH) 2 (trace 
Ni(OH) 2 ). 
Confirm Mn. 

(а) Borax bead 
—O.F. amethyst 
purple. R.F. 
colorless. 

(б) Confirm by 
lead oxide 
method. (See 
Procedure A.) 


Filtrate.— 

Na 2 + Zn0 2 —. 
Pass in H 2 S. A 
white precipitate 
indicates Zn. 

Confirm by ash 
test with cobalt 
nitrate. 

(See Procedure 
A.) 


Notes on Procedure B 

This method takes advantage of the fact that aluminum, chromium, and 
iron are precipitated as hydroxides in solutions made alkaline with NH 4 OH 
in the presence of NH 4 C1. 

The hydroxides of chromium and zinc are soluble in NaOH, whereas 
Fe(OH) 3 is insoluble, hence the latter may be removed from the former by 
the method given. 

In the removal of phosphoric acid, chromium and aluminum may be 
precipitated with the phosphate. They may be tested for by suspending 
the precipitate in water and adding Na 2 0 2 to strong alkalinity and filtering. 


Residue.—Fe(OH) 3 , etc. 


Filtrate.—Contains aluminum and chromium. 
Divide into two portions. Acidify one portion 
with acetic acid and add lead acetate. A yellow precipitate is PbCr0 4 . To 
the other portion add HC1 to acidity and then make alkaline with NH 4 OH 
and boil. A gelatinous, white precipitate is Al(OH) 3 . 










QUALITATIVE ANALYSIS 


122 


I. 


The Basic Acetate Method of Analysis of (NH 4 ) 2 S Group 
Optional Procedure C 


Oxidize the iron in filtrate of the H 2 S Group (from which H 2 S has been 
expelled by boding) by boiling with 2-3 cc. HN0 3 (1.24). Add 5 cc. of NH 4 C1, 
if not already present; and then NH 4 OH until just alkaline. (A slight pre¬ 
cipitate will form if Fe, Al, or Cr are present.) If iron is present, it can be 
recognized by the reddish color of the trace of precipitate that forms. If not 
reddish brown, dissolve in a few drops of HC1, add a little FeCl 3 solution 
and again neutralize. Now dissolve (if enough iron has been added) in a drop 
or so of HC1 and add ammonium acetate (10-15 cc. 4 N sol.); dilute with 
hot water to about 500 cc., boil and filter; wash free of acid with hot water. 


II. 


^ Precipitate.—Fe(0H) 2 C 2 H 3 0 2 ; A1(0H) 2 C 2 H 3 0 2 ; Filtrate.—I o n s of 
Cr(0H) 2 C 2 H 3 0 2 . Iron has already been indicated. Ni,Co,Zn,Mn. Seelll. 
Divide into two portions (o) and (6). --:- 


(a) Add 5-10 cc. H 2 0 and Na 2 0 2 in 
small portions. 

(6) Add 10 cc. NaOH and boil and 
filter. 

Residue.—Fe, reject. Filtrate.—Cr. 

Residue.—Fe, reject. Filtrate.—Al. 

Acidify the Na 2 Cr0 4 with acetic acid. 
A transient blue HCr0 3 indicates 
chromium. 

Confirm by evaporating to dryness 
and precipitating PbCr0 4 yellow in 
acetic acid solution. 

Acidify with HC1 (1.12), make just 
alkaline with NH 4 OH. A white floc- 
culent precipitate is due to Al(OH) 3 . 
Confirm by the Co(NO s ) 2 test. 

Blue residue is C 0 AIO 2 . 


III. 

Filtrate from the Acetates of Al, Cr, and Fe.—Concentrate to about 
100 cc. Make just alkaline with NH 4 OH. Heat to boiling and add 5—10 cc. 
(NH 4 ) 2 S; filter, and wash with hot water containing a little H 2 S and NH 4 C1 
until free from alkali. 


Precipitate.—NiS, CoS, MnS, ZnS. Add 10-30 cc. Filtrate.—Ions of 
cold HC1 (1.12), digest, stirring thoroughly, filter, and the following groups, 
wash residue with water containing H 2 S.-— 























THE METALS 


123 


IV. 


Residue.—NiS, CoS. 
Test and separate ac¬ 
cording to methods 
already studied. 


Filtrate.—ZnCl 2 and MnCl 2 . Boil to expel H 2 S, 
make just alkaline with NaOH, shake and filter. 


Precipitate.— 

___Mn(OH) 2 , first light 

colored, changing to 
brown. (Ni and Co may be present.) 

Confirm.—Fuse in Pt loop with Na 2 C0 3 . A dark- 
green bead is NaMn0 4 . (Light green may be due 
to Ni.) 


Filtrate.—N a 2 ZnO 2 . — 
Acidify with acetic acid 
and pass in H 2 S. A white 
ppt. is ZnS. 

Confirm with Co (NO 3 ) 2 
test. CoZn0 2 , green. 


Notes on Procedure 

Chromium is precipitated on boiling as the basic acetate only in 
presence of relatively large amounts of ferric iron and aluminum. If Cr 
is present in relatively large amount and Fe and A1 only in small amount 
the precipitation of the basic acetates is incomplete. 

The excess of Fe also removes any P0 4 that may be present. 

NiS is soluble in excess of NH 4 OH, hence this is avoided. 

NH4CI prevents colloidal solutions forming. 

ZnS in acetic acid solution is less apt to be contaminated than in alkaline 
solution. 









124 


QUALITATIVE ANALYSIS 


CLASSROOM REVIEW 

1. What general substances interfere in the precipitation and separator 
of this group. Why? How may these be removed? 

2. What reactions are common to all the members of the Ammonium 
Sulphide Group? 

3. Make a comparative study of the general methods of analysis given 
What are their relative merits? 

4. Devise another method for the separation of nickel from cobalt. 

5. Why are the carbonates and sulphides of ferric iron and of chromium 
and aluminum decomposed by water? 

6. (a) In what way do organic compounds interfere with the analysis of 
this group? 

(b) Why does the presence of the phosphate anion interfere? 

7. Why is not magnesium precipitated by ammonium hydroxide when 
ammonium chloride is present in the solution? 

8. Why does a solution of K 4 Fe(CN) 6 fail to give the ordinary tests for 
iron? 

9. Be prepared to give reasons for each of the processes used in the separa¬ 
tion of the ions and the condition of the cations in the different stages they 
pass through before they are finally isolated and recognized. 

10. How are the sulphides of nickel and cobalt separated from the other 
members of the group? 

11. How are the hydroxides of manganese and iron separated? 

12. Could you use the Hydroxide Method B when aluminum is present 
in large amount and zinc in small amount, say in a ratio of 9 to 1. Give 
reason for your answer? 

13. How would you distinguish between ferrous and ferric iron? 

14. How would you distinguish a chromic salt from a chromate? 

15. What is the purpose of adding Na202 in the first procedure A of 
separating the group? 

16. Write out the reactions involved in the course of analysis of a mixture 
containing the elements of this group; show the compounds formed with the 
addition of each reagent in the process of separation of the elements, e.g. 
trace the different phases an element passes through during its isolation and 
final identification, 










AMMONIUM CARBONATE GROUP 

Alkaline Earths, Group 4 

Common Elements. —Barium, Calcium, Strontium. 

1 eneral Characteristics. 

The group contains the alkaline earth metals, barium, calcium 
nd strontium, which are distinguished from the metals of preced- 
ig groups by the fact that their salts are not precipitated by 
IC1, H 2 S or (NH 4 ) 2 S, and are distinguished from the metals 
f the following groups by the fact their ions are precipitated as 
arbonates by ammonium carbonate in alkaline solutions in the 
jresence of ammonium chloride. The elements are comparatively 
oft metals. They oxidize in the air, decompose water, forming 
lydroxides and liberating hydrogen. Their salts are similar. 
VIost of these are white or colorless with exception of those whose 
icid radical imparts a color. The sulphides exist only in dry 
state; when treated with water H 2 S is evolved and the hydroxides 
}f the elements are formed. The members of the group are 
bivalent. 

Individual Characteristics. 

BARIUM 

Ba, at.wt. 137.37 ; sp.gr. 3.78 ; m.p. 860° C. ; volatile at 950° C. ; oxides, 
BaO, BaOa 

The metal is pale yellow. Its properties are similar to those of calcium 
and strontium. It is more readily oxidized in the air than either of its com¬ 
panion metals, and it decomposes water more readily. Its ores are not as 
common as those of calcium. It never occurs free in nature. The salts that 
are practically insoluble in water are BaSO*, BaCr0 4 , BaC0 3 , BaGaO«. 

The silicate BaSiF* is slightly soluble. See list of compounds in Part V. 

125 



126 


QUALITATIVE ANALYSIS 


Solubility.—Compounds of barium with the exception of the sulpha 
BaS0 4 , are soluble in hydrochloric and nitric acids. The sulphate is solul 
in hot concentrated sulphuric acid, but is reprecipitated upon dilution of t 
solution. The sulphate is best fused with sodium carbonate, which tra] 
poses the compound to barium carbonate; sodium sulphate may now 
leached out with water and the residue, BaC0 3 , then dissolved in hyd 
chloric acid. 

DETECTION 

Preliminary Tests.—Much time may be saved by making a prelimina 
test for barium, strontium, and calcium by means of the spectroscope a 
avoiding unnecessary separations. By this means one-thousandth of a mi] 
gram of barium, six hundred-thousandths of a milligram of strontium or c; 
cium may be detected. The characteristic spectra of these elements are giv 
in the chart, Plate I, Frontispiece. 

Barium is precipitated as the carbonate together with strontium and cs 
cium, by addition of ammonium hydroxide and ammonium carbonate to t 
filtrate of the ammonium sulphide group. It is separated from strontiu 
and calcium by precipitation as yellow barium chromate, BaCr0 4 , from 
slightly acetic acid solution. 

Saturated solutions of calcium or strontium sulphates precipitate whi 
barium sulphate, BaS0 4 , from its chloride or nitrate or acetate solutio 
barium sulphate being the least soluble of the alkaline earth sulphates. 

Soluble chromates precipitate yellow barium chromate from its neutr 
slightly acetic acid solution, insoluble in water, moderately soluble in chrom 
acid, soluble in hydrochloric or nitric acid. 

Fluosilicic acid, H 2 SiF 6 , precipitates white, crystalline barium fluosilicat 
BaSiFe, sparingly soluble in acetic acid, insoluble in alcohol. (The fluosi 
cates of calcium and strontium are soluble.) 

Flame.—Barium compounds color the flame yellowish green, which appea 
blue through green glass. 

Spectrum.—Three characteristic green bands (a, p, 7 ). Faint bands aL 
in the red field of the spectrum. 

Barium sulphate is precipitated by addition of a soluble sulphate to a soli 1 
tion of a barium salt. The compound is extremely insoluble in water an i 
in dilute acids (soluble in hot concentrated sulphuric acid). The sulphate 
readily distinguished from lead sulphate by the fact that the latter is solub] 
in ammonium salts, whereas barium sulphate is practically insoluble. 






THE METALS 


127 


CALCIUM 

ih 

Ca, at.wt. 40.07; sp.gr. 1.5446 290 ; m.p. 810° C.; oxide, CaO 

a The element is silvery white and harder than lead. It decomposes water, 
derating hydrogen and forming calcium hydroxide. 

fr The following salts are practically insoluble in water, CaC 2 04 , CaC0 3 , 
aF 2 , Ca 3 (P 0 4 ) 2 . Their degree of solubility may be found in the list of 
iilcium compounds given in Part V. 

The oxide, hydroxide, and salts of calcium are soluble in acids with the 
deception of gypsum and certain silicates which require fusion with sodium 
&hrbonate or bicarbonate followed by an hydrochloric acid extraction. 

DETECTION 


V£ General Procedure.—In the usual course of qualitative and quantitative 
aalysis calcium passes into the filtrates from the elements precipitated by 
hydrogen sulphide in acid and alkaline solutions (Ag, Hg', Hg", Pb, Cu, Cd, 
tt a> Sb, Sn, Fe, Cr, Al, Mn, Ni, Co, Zn, etc.), and is precipitated from an 
H'tnmoniacal solution by ammonium carbonate as calcium carbonate, along 
l ith the carbonates of barium and strontium. The separation of calcium 
om barium and strontium is given on page 134. The oxalate of calcium 
i J i the least soluble of the alkaline-earth group. All, however, are soluble 
n mineral acids. Calcium oxalate may be precipitated from weak acetic acid 
olution by ammonium oxalate. 

r Flame Test.—The flame of a Bunsen burner is colored yellowish red when 
i platinum wire containing calcium salt moistened with concentrated hydro- 
hloric acid is held in the flame. 

t Spectrum.—An intense orange and green line with a less distinct violet 

1 ine. Note chart of the spectra of the alkaline earths. Plate I. 


STRONTIUM 

Sr, at.wt. 87.63; sp.gr. 2.54; m.p. 900° C; oxides SrO and Sr0 2 

Strontium is a soft yellow metal with properties very similar to those of 
mrium and calcium. The metal occurs only in combined state in nature, 
[ts minerals are not as abundant as those of calcium. 

The salts SrC0 3 , SrC 2 0 4 , SrS0 4 are the least soluble of strontium salts. 
\ fist of compounds may be found in Part V. 

DETECTION 

General Procedure.—Strontium is precipitated with barium and calcium, 
in the filtrate, from the ammonium sulphide group, by addition of ammonium 




128 


QUALITATIVE ANALYSIS 


carbonate to the ammoniacal solution. The precipitate is dissolved in acet 
acid and treated with potassium dichromate, and the barium filtered off ; 
BaCr(> 4 . Strontium and calcium in the filtrate are separated from the exce 
of potassium chromate by reprecipitation as carbonates by the addition 
ammonium carbonate, the precipitates are dissolved in acetic acid and tl 
excess of free acid neutralized with ammonia. Strontium may now be pr 
cipitated from the concentrated solution by boiling with an equal volume of 
saturated solution of calcium sulphate. 

Sodium Sulphate Test.—A saturated solution of the salt added to a soli 
tion containing strontium chloride, made strongly acid with acetic acid, an 
the mixture boiled, will produce a distinct precipitate if strontium excee( 
0.0015 normal. Calcium does not precipitate until 1.3 normality is reaches 

Flame Test.—Strontium, preferably in the form of the chloride, in a hydr< 
chloric acid solution, placed on a platinum loop and held in a colorless flam 
colors the flame crimson. (Lithium gives a red color, calcium a yellowish-red 
The test is best confirmed by means of the spectroscope. 

The Spectra of Strontium.—Eight bright bands; 6 are red, 1 orange, 1 blu 
Two of these, known as strontium /3 and y, are red, the orange is strontium 
and the blue strontium 5. The delicacy of the test is 0.6 m illi gram Sr per c 
The test is very much more delicate with the arc spectra, e.g., 0.03 milligrai 
Sr per cc. 






THE METALS 


129 


LABORATORY EXERCISES 

Chemical Reactions of the Ammonium Carbonate Group 

BARIUM, Ba + + 
ft 

I A. Wet Tests.— Use BaCU solution for the tests. 

1 . Precipitate BaC 03 from a solution made alkaline with 
H4OH by adding (NH^CCb solution. 

Reaction.—BaCl 2 + (NH 4 ) 2CO3 = 1 BaC0 3 (white) +2NH 4 C1. 

2. Note that the precipitate is insoluble in NH4CI, but dis- 
lves in acetic acid. 

Reaction.—BaCOsd^HCaHsC^ = Ba(C2H 3 02)2'j - T C02 _ } _ H20. 

1 

11 3. To the solution containing barium acetate add K 2 Cr 04 . 
11 he precipitate is BaCrCU, light yellow. What advantage can be 
ken of the insolubility of the chromate of barium in acetic acid? 

Reaction.—BaCl 2 +K 2 Cr 04 = 1 BaCr0 4 (yellow) +2KC1. 

Note. —Chromates of calcium and strontium being soluble make it possible 
separate barium from these elements by precipitation as BaCr0 4 and 
tering off Sr and Ca. 

4. Filter off the precipitate and dissolve by adding a few drops 
dilute HC1, dilute with water and add half a cc. of dilute 
2 SO 4 . The white precipitate is BaSC>4. 

Reaction.—BaCl 2 4-H2S0 4 = BaS0 4 +2HCl. 

5 . To a fresh portion of the BaCU solution add a few drops 
a saturated solution of CaS 04 . 

Reactions.—BaCl2+CaS04 = 1 BaS04+CaCl2- 

6 . To another portion add a saturated solution of SrS 04 . 

Reaction.—BaCl2+SrS04 = I BaS 04 +SrCl 2 . 




130 


QUALITATIVE ANALYSIS 


The precipitate of BaS 04 is a proof that it is less soluble th 
either CaSC>4 or SrSC>4. 

7. Barium sulphate is insoluble in alkalies, but boiled with 
strong solution of Na 2 C 03 the sulphate is partially transposed 
BaCC> 3 , the reaction being the reversible. 

Reaction.—BaS0 4 +Na 2 C0 3 ^ 1 BaC0 3 +Na 2 S0 4 . 

By fusing the sulphate of barium with several times its weig 
of sodium carbonate the transposition is complete. The sodii 
sulphate may be extracted with water and the residue, BaC(. 
then dissolved in dilute HC1. 

8. Add ammonium oxalate reagent to another portion 
BaCb solution. With barium exceeding 0.006 gram per 100 < 
of solution a white precipitation of BaC 2(>4 is obtained. 

BaCl i + (NH 4 ) 2 C 2 0 4 = i BaC 2 0 4 +2NH 4 Cl. 

9. The precipitate is soluble in dilute mineral acids and 
boiling acetic acid. (CaC 204 is insoluble in hot acetic acid, SrC 2 
sparingly soluble.) 

10. Na 2 HP 04 precipitates BaHPCU from neutral solutions a 
Ba 3 (P 04)3 from ammoniacal solutions. The precipitate dissolv 
readily in acid solutions, including the weak acetic acid. 

Reactions.—(a) BaCI 2 +Na 2 HP0 4 = 1 BaHP0 4 +2NaCl. 

(6) 3BaCl 2 +2Na 2 HP0 4 +2NH 4 0H = 

1 Ba 3 (PO 4 ) 2 +4N aCl-f2NH 4 C1+2H 2 0. 

B. Dry Tests. 11. Test a portion of solid BaCl 2 with 
flame test, first moistening the platinum wire used for the test wi i 
HOI. The color of the flame appears a light green. In preser 
of sodium the color appears a yellowish green. 

12. Examine flame by means of the spectroscope. Note t 
colored chart Plate I for characteristic lines seen by means 
the spectroscope. 








THE METALS 


131 


CALCIUM, Ca+ + 

jj A. Wet Tests.— Use CaCU for the tests. 

I 13. Add a few drops of NH 4 OH and then about 5-10 cc. 
(NH 4 ) 2 CO 3 solution. The precipitate is CaC03. 


Reaction.—CaCl 2 +(NH 4 ) 2 C0 3 = i CaC0 3 (white) +2NH 4 C1. 

14 . Note the precipitate dissolves in dilute mineral acids and 
acetic acid. 

15 . Add 2 cc. NH4CI and heat to boiling. Does the pre- 
>itate dissolve? 

16 . Pour on a filter paper and dissolve the precipitate by pour- 
* over it about 5 cc. hot acetic acid (30 per cent). To 2-3 cc. 
C :Cr04 solution add several drops of the calcium acetate solution. 
Ipfes a precipitate form? 

Reaction.—CaC0 3 +2H-C 2 H 3 0 2 = Ca(C 2 H 3 0 2 ) 2 + T C0 2 +H 2 0. 


17 . Now pour several drops of a fresh solution of CaCl2 into 
■ out 5 cc. of NH4C2O4 solution. Does a precipitate form? 


Reaction. 


— CaCl 2 -b£ NH j£2°4 = 1 CaC 2 0 4 +2NH 4 Cl. 


• 18 . Add a few drops of CaCU solution to a saturated solution 
(NU4) 2SO4 and note whether a precipitate forms. 

From a concentrated solution, dilute H2SO4 or an alkali sul- 
late, precipitates CaS04, soluble on dilution, and appreciably 
luble in a hot concentrated solution of (NH4)2S04 (distinction 
)m Ba and Sr). 

19 . Make another portion of the solution alkaline with NH 4 OH 
id precipitate the carbonate of calcium by the addition of 
IH4)2C03 solution. Filter. Pour over the filter a few drops 
HNO3 to dissolve the precipitate, catching the soluble nitrate 
an evaporating dish. Evaporate nearly to dryness and add 
10 cc. of amyl alcohol; stir up with the residue and pour into 
large test tube. Insert a thermometer and heat the solution to 
;0°. Does the salt dissolve in the amyl alcohol? 





132 


QUALITATIVE ANALYSIS 


The solubility of calcium under this treatment is a method 
separation from strontium which remains as a residue of SrN 
when the mixture is filtered. 

20. Dilute with an equal volume of ethyl alcohol and ad< 
few cc. of dilute H2SO4. The white precipitate is CaSCU. 

Reaction.—Ca(N 0 3 ) 2 +H 2 S 04 = J. CaS0 4 (white) +2HN0 3 . 


21. Disodium phosphate. The reaction is similar to that 
Barium with this salt. 

B. Dry Tests. 22. Test a little of the solid CaCl 2 in the fla 
and note color, dipping the test wire of platinum first in HC1. 

The flame is colored yellowish-red by the calcium salt. 

23. Examine the flame by means of a spectroscope and n 
the spectrum of Ca. 

See colored chart for characteristic lines seen by means of 
spectroscope. 

STRONTIUM, Sr+ + 

A. Wet Tests. Use SrCE solution for the tests. . 

24. Make the same tests indicated for calcium. Note tl 
SrC 03 dissolves in HNO 3 , but the nitrate salt, formed up 
evaporation, is insoluble in amyl alcohol. Pour the precipit;' 
on a filter. 

Reactions.—(a) SrCl 2 +(NH 4 ) 2 C0 3 = j SrC0 3 (white) +2NH 4 C1. 

(6) SrC0 3 +2HC 2 H 3 0 2 = j Sr(C 2 H 3 0 2 ) 2 + T C0 2 +H 2 0. 

(c) SrCl 2 + (NH 4 )_C 2 0 4 = j SrC 2 0 4 +2NH 4 Cl. 

Note. —SrC 2 0 4 is only sparingly soluble in acetic acid, but dissol; 
readily in dilute mineral acids. (See Barium, Exp. 9.) 


25. Dissolve the precipitate in a few drops of water. To 
solution add a few drops of a saturated solution of CaSC^. 
white precipitate is SrSO.*. 

Sr(N0 3 ) 2 +CaS0 4 = J SrS0 4 (white) +Ca(N0 3 ) 2 . 




THE METALS 


133 


Note. —SrS0 4 is practically insoluble in a strong solution of hot (NHOiSO^ 
This affords a precedure for separating strontium from calcium, as the sulphate 
r of the latter dissolves in strong hot solution of ammonium sulphate. The 
separation, however, is not complete, so that a confirmatory test is necessary. 

26. To another portion of SrCl 2 solution add a few drops of 
* NH4OH and then K 2 OO 4 . Does a precipitate form? Now add 
4-5 cc. of ethyl alcohol. Does this cause a precipitate to form? 

The solubility of the chromate affords a method for separating 
strontium from barium. 

B. Dry Tests. 27. Test a portion of the strontium salt (solid) 
t with the flame test. 

The platinum wire used for the test is dipped into HC1 and 
then into the salt to be examined. The flame is colored crimson 
or deep red by strontium salts. 

28. Examine the flame by means of the spectroscope. 

Consult the colored chart for the characteristic lines seen 
through the spectroscope. 


Table of Reactions 

Turn to the table of comparative reactions for the ammonium carbonate 
groups, making the tests indicated here, which have not been given under the 
exercises above. 



134 


QUALITATIVE ANALYSIS 


Outline of the Method of Separation and Detection of the 
Ammonium Carbonate Group 

By means of the flame test it is possible, with a little practice 
to detect the members of this group. The characteristic color 
do not appear at the same time owing to the difference in tb 
volatility of the chlorides of barium, calcium and strontium 
Examination of the flame by means of the spectroscope establishe 
with certainty traces of these elements in the solution examined 
These tests are valuable for confirmation of these elements. 

A rapid preliminary examination of the solution may be mad< 
on three portions. The fact that SrS0 4 and BaS0 4 are less solubli 
than CaS0 4 enables us to detect one or both of these element; 
by addition of a saturated solution of CaS0 4 to the concentratec 
solution of this group. The precipitate may consist of one o: 
both of these sulphates. Should a precipitation occur, a seconc 
portion is examined for Ba and Sr by means of K 2 Cr0 4 . BaCrCX 
will precipitate and Sr may be found, if present, in the filtrate b} 
precipitation with CaS0 4 . Calcium is detected in a third portior 
by precipitation as CaC 2 0 4 after removal of the less solubl< 
sulphates with H 2 S0 4 . 

In the general procedure if the solution examined is the filtrate 
from the ammonium sulphide group, a sufficient amount of NH 4 C 
will be present to prevent precipitation of MgC0 3 with carbonates 
of Ba, Ca and Sr. In an original solution it will be necessary tc 
add NH 4 C1. The members of the group are precipitated in 
presence of NH 4 C1 by addition of (NH 4 ) 2 C0 3 to the ammoniacal 
solution containing the group. The alkalies, if present, are j 
removed by filtration. The precipitate is dissolved in acetic acid 
*and from the solution, diluted, BaCr0 4 is precipitated by adding 
K 2 Cr0 4 . Calcium and strontium do not precipitate and will 
pass into the filtrate. To remove the excess K 2 Cr0 4 , CaC0 3 
and SrC0 3 are again precipitated. The carbonates washed free 
of the reagents are brought into solution as nitrates or acetates 




THE METALS 


135 


,nd detected by one of two optional methods given. The first 
>rocedure takes advantage of the insolubility of SrN0 3 in 100 
>er cent amyl alcohol; CaN0 3 being soluble a separation is effected. 
The elements are now confirmed. 

[• In the second procedure the carbonates of Ca and Sr are con¬ 
certed to the soluble acetates. SrS0 4 is precipitated by addition 
of a saturated solution of (NH 4 ) 2 S0 4 , calcium remaining in solu- 
s:ion. The sulphate of strontium may now be dissolved in HC1 
and the flame test made. CaC 2 0 4 is precipitated from an am- 
aioniacal solution and further confirmed by testing its solubility 
3 in dilute acetic acid and by the flame test. 


Rapid Preliminary Examination for Barium, Strontium, and Calcium 

Make a mixture of the chloride solutions of barium, strontium, and cal¬ 
cium, using about 5 cc. of each. Divide into three portions, A, B, C. 


A. Calcium Sulphate 
test for Strontium and 
Barium. 

Add about four vol¬ 
umes of a saturated solu¬ 
tion of CaS0 4 to portion 
A. The precipitate con¬ 
sists of BaS0 4 and SrS0 4 . 
These sulphates are both 
less soluble than that of 
calcium. 


B. Detection of Ba¬ 
rium and Strontium in 
a mixture. 

Test A indicates the 
presence of strontium or 
barium or both. Test 
B is to detect each. Add 
to the solution a slight 
excess of K2Cr0 4 . A 
yellow precipitate indi¬ 
cates BaCr0 4 . Filter 
and add to the filtrate 
2-3 cc. of a saturated 
solution of CaS0 4 . A 


C. Detection of Cal¬ 
cium in a mixture of the 
soluble salts of the group. 

Add a few drops of 
H 2 S0 4 as long as a pre¬ 
cipitate forms. Filter 
and to the filtrate add 
NH 4 OH to alkalinity 
and then a solution of 
(NH 4 ) 2 C 2 0 4 . A fine, 
white precipitate insolu¬ 
ble in dilute acetic acid 
is CaC 2 0 4 . 


white precipitate indi¬ 
cates the presence of 
Strontium. 














136 


QUALITATIVE ANALYSIS 


Separation of the Ammonium Carbonate Group 

I. Acidulate the filtrate of the Ammonium Sulphide Group with HC1, anc 
evaporate to 15-20 cc. (If previous groups have not been sought, add 5-l( 
cc. of NH4CI solution.) Filter if the solution is turbid to remove the fre< 
sulphur. To the clear solution add NH 4 OH, drop by drop, until the solutioi 
is alkaline. Heat to boiling and add to the hot solution (NH 4 ) 2 C0 3 in smal 
portions at a time as long as a precipitate continues to form (20-30 cc/ 
Keep the mixture hot for five minutes, then filter and wash with small portion; 
of hot water. 

II. 


Filtrate may contair 
Mg++, Na+, K+, Li+ 
NH 4 + , acid radicals, traces 
of Ba ++ , Ca ++ , anc 
Sr + + . 


Precipitate.—White,—CaC0 3 , BaCO s , SrC0 3 . 

Dissolve the precipitate on the filter by pouring 
over it 10-20 cc. hot acetic acid (30 per cent solu¬ 
tion). Repeat the operation with the filtrate if 
necessary. Test a small portion of the filtrate with 

K 2 OO 4 . If a precipitate forms, add to the re--—- 

mainder of the solution about 5 cc. NaC 2 H 3 0 2 and then K 2 Cr0 4 , drop by 
drop, as long as a precipitate continues to form. The supernatant liquic 
should be slightly yellow to indicate an excess. Warm the solution. Allow 
the precipitate to settle and filter. (In case the blank test gives no precipi¬ 
tate, omit the addition of the chromate and proceed to the tests for strontium 
under IV.) 


III. 


Precipitate.—Light yellow, BaCr0 4 . Dissolve in dilute 
HC1 and add an equal volume of a saturated solution of 
SrSO 4 (any soluble sulphate will do). A white precipitate 
is BaS0 4 . Further confirmation may be made with flame 
and spectroscopic tests. 


treat with NH 4 OH and (NH 4 ) 2 C0 3 , as indicated above, 
the carbonate, boil, filter, and wash. 

IV. 


Filtrate —Ca + + : 
Sr++, C 2 H 3 0 2 - 

CrO.—. 

Refilter if the 
solution is not clear. 
Boil the filtrate and 
Add 5 cc. more ol 


Precipitate.—SrC0 3 , CaC0 3 . 

Preliminary Test for Strontium.—Dissolve a small portion of the precipi¬ 
tate in a few drops of warm acetic acid and dilute to 5 cc. Test the strontium 
by adding a saturated solution of CaS0 4 . If no precipitate forms, test the 
remainder of the solution for calcium according to the procedure for calcium 
under Va or V6. If strontium is present, follow directions for separation 
under either Vo or V6. 

















THE METALS 


137 


V a Separation of Strontium and Calcium 


j Dissolve the precipitate SrCOs and CaC 03 in a few 
drops of dilute HN0 3 , and evaporate almost to dry- 
6 ness in a porcelain dish. (If Ba is absent (test under 
a II), add 2 cc. cone. HNOs and evaporate to dryness to 

1 expel acetic acid; take up with a few drops of HN0 3 1 
10 cc. of amyl alcohol, stir and transfer to a test tube, 
s eter. Boil until the temperature rises to 130°, ad 
replace that which evaporates if the volume decreases i 
through a dry filter. 

Filtrate. — Cr0 4 , 
C 2 H 3 0 2 “. Reject the 
solution. 

and reevaporate.) Add 
, and insert a thermom- 
ding more alcohol to 
;o less than half. Filter 

Residue.—Sr (NO 3) 2 . Rinse the residue 
into a test tube with absolute alcohol. De¬ 
cant the clear supernatant liquid through a 
filter into the solution to be tested for cal¬ 
cium. 

Confirm strontium by the flame and the 
spectroscope. 

The salt dissolved in a few drops of water 
and poured into a saturated solution of 
CaSO 4 will produce a white precipitate of 
SrSO 4 if the solution contains strontium. 

Solution. — Ca ++ 2N0 3 ~. 
Dilute with an equal volume of 
ethyl alcohol and add dilute 
H 2 SO 4 . A white, flocculent pre¬ 
cipitate, CaSO 4 , indicates Cal¬ 
cium. 

Confirm by flame and spec¬ 
troscopic tests. 

V b Optional Method for the Separation of Strontium and Calcium 

Dissolve the precipitate SrCO, and CaCOs in a few drops of warm acetic 
acid and dilute to 5 cc. Add a saturated solution of (NH 4 ) 2 S0 4 ; boil and 
filter. 1 

Precipitate. — SrSO 4 , 
white. Confirm by 

flame test, etc. 

Filtrate. — Ca + + , etc. Make alkaline with NH 4 OH 
and add a solution of (NH 4 ) 2 C20 4 . A white precipi¬ 
tate insoluble in acetic acid is CaC 2 0 4 . 2 Confirm by 
the flame test. 


11 Separation of the sulphates of strontium and calcium in a hot 
iturated solution of (NH,) 2 SO, is not complete, since a little CaSO, 
amains with SrSO, and some SrSO, goes into solution with CaSO,, hence 
onfirmatory tests are necessary. 

^ Solubility CaC 2 0,-H 2 0 = 0.000554 gram per 100 cc.H 2 0. BaC 2 0,-H 2 0 

=0.0093 gram. sAo,-H 2 0 = 0.0051 gram. MgC 2 0,2H 2 0=0.07 gram. 


























138 


QUALITATIVE ANALYSIS 


Notes on the Analysis of the Ammonium Carbonate Group 

I. On boiling the filtrate from the Ammonium Sulphide Group free sulphu 
will separate out and cause the solution to become turbid. Filtration wil 
remove this. 

An excess of NH 4 C1 should be avoided, as it will not only dissolve mag 
nesium salts, but also cause the carbonates of calcium, strontium, and bariun 
to dissolve. If too much NH 4 C1 is present, the solution should be evaporatec 
to dryness and heated to expel ammonium salts, the residue taken up wit! 
water, and the analysis made for the group. 

Boiling the solution renders the carbonates of the group less soluble by 
preventing the formation of the soluble bicarbonates. Allowing the solutior 
to stand for five minutes lessens the possibility of the precipitate passing 
through the filter. (See Introduction.) 

Traces of calcium, strontium, and barium may pass into the Soluble Group 
solution. They should be tested for and removed before making the test 
for magnesium. 

II. By testing a portion of the filtrate containing the acetates it can be 
determined whether it is necessary to add potassium chromate to the solution. 
Since this has to be removed in order to separate the elements strontium and 
calcium by the method here given, time will be saved by avoiding its addition 
if barium is absent. A method of separating strontium from calcium in the 
presence of Cr0 4 anion is given by William C. Bray in The Journal oj 
the American Chemical Society , June, 1909. His method of separation is 
practically as follows: The solution containing Ca++, Sr++, and CaHiOa - 
together with Cr0 4 is made alkaline with NH 4 OH with 2-3 cc. in 
excess, then diluted to 60 cc. and 50 cc. of 95 per cent alcohol added. j 
Strontium separates as a chromate, while calcium passes into the filtrate. 

The addition of the chromate, drop by drop, in the precipitation of barium | 
prevents the occlusion of calcium or strontium and insures the complete | 
precipitation of barium. An excess of the reagent colors the solution yellow, 
showing that the precipitation is complete. 

III. The reprecipitation of the strontium and calcium as carbonates is for 
the purpose of removing the chromate radical. This section is omitted if the 
preliminary test proves barium to be absent; in which case K 2 Cr0 4 is not 
added. 

IV. The preliminary test may be made quickly, the time gained in avoid¬ 
ing an unnecessary procedure for separation in absence of strontium makes 
this test advisable. 

Va. In this method of separating strontium and calcium, advantage is taker 
of the insolubility of strontium nitrate in amyl alcohol and absolute ethy 
alcohol. Since amyl alcohol is apt to contain water, which would dissolve 






THE METALS 


139 


the precipitate, the solution is heated to 130° to drive off the water. The 
alcohol boils at this temperature. The calcium salt is soluble in amyl alcohol. 
r V6. The optional method takes advantage of the solubility of CaS0 4 in a 
^strong solution of ammonium sulphate. Strontium is precipitated by this 
reagent as the sulphate, SrS0 4 . 

The flame and spectroscopic tests for strontium and calcium are necessary 
] for confirmation. The platinum wire, used for making the tests, should 
1 impart no color to the flame when dipped in pure cone. HC1 and held in the 
1 flame. The wire may be cleaned by dipping in HC1 and holding in the flame 
repeatedly until the impurities have volatilized, the final acid treatment 
f being with fresh acid. The acid should be poured in a dish for use in the flame 
1 tests; never insert the wire in the reagent bottle. 

! Magnesium.—In the system of analysis of the group by W. C. Bray, 

magnesium is included in the group, being precipitated as a double ammonium 
1 magnesium carbonate from a cold solution containing an excess of ammonium 
: carbonate in the absence of ammonium chloride. Magnesium remains in 
the filtrate with calcium after the removal of barium and strontium as chro- 
1 mates. It is separated as follows: The strontium filtrate is diluted to 250 cc. 
with water heated to boiling and about 50 cc. of ammonium oxalate added. 
Calcium precipitates as an oxalate, and is thus removed. Magnesium is 
precipitated from the solution, made alkaline with NH 4 OH by the addition 
of disodium phosphate. The addition of alcohol hastens precipitation, as it 
renders the precipitates less soluble, thus preventing a reverse reaction. (See 
Introduction.) 

CLASSROOM EXERCISES 

1. Turn to the Table of Reactions in Part V, and from the solubilities of 
the salts devise another method of separating the members of the Ammonium 
Carbonate Group. 

2. What are the following substances: Plaster of Paris? Bleaching 
powder? Baryta water? Superphosphate of lime? Lime water? Barium 
peroxide? Heavy spar? Gypsum? Mortar? Lime and slaked lime? 

3. What use is made of the members of this group in pyrotechnics? 

4. What reactions are common to the members of this group? 

5. Give a method by which each member of the group may be extracted 

from its mineral. 

6. Trace the changes that take place with each element during the process 
of analysis, writing out the equations representing the reactions that take 

place with the addition of each reagent. ... 

7. Why must ammonium chloride be present during the precipitation 

of the group? 

8. Describe the procedure for making a flame test. 






SOLUBLE BASIC GROUP 

The Alkalies, Sodium Group, Group 5 

Common Elements.—Magnesium, Sodium, Potassium, Amm oni um . 

Rare Metals.—Lithium, Caesium, Rubidium. 

General Characteristics. 

The members of this group derive their name from the fact 
that their ions, in the presence of ammonium chloride, do not ! 
form insoluble salts with any of the precipitating reagents thus ' 
far used, nor do they have a common precipitating anion. Nearly 
all their salts are soluble and readily ionized in solution. This 
fact prevents a satisfactory separation, as in case of the groups 
thus far studied. The solubility of magnesium salts places this 
element with the alkalies, although it is classed in the periodic 
table with the alkaline earths, and possesses characteristics more 
in common with that group—Ca, Sr, and Ba. Its hydroxide, 
carbonate and phosphate are insoluble in water, but dissolve 
in presence of NH 4 C1. The presence of NH 4 CI prevents the 
precipitation of magnesium carbonate with the members of the 
ammonium carbonate group. Lithium, sodium, potassium, rubid¬ 
ium, caesium, and ammonium have common characteristics, 
being grouped together as the alkali metals. They do not occur 
free in nature. Their compounds are widely distributed in nature, 
occurring commonly in mineral or salt waters and in many rocks; ' 
only sodium and potassium, however, are abundant. The ele¬ 
ments are soft, light metals that are easily melted, their melting- 
points decreasing and their densities increasing with the rise of 
their atomic weights. The metals possess a silver lustre, and are 
easily tarnished in the air owing to oxidation. They readily 
decompose water, forming strongly basic hydroxides with the 

140 



THE METALS 


141 


jeration of hydrogen. They are all univalent (Mg bivalent), 
tieir carbonates and phosphates are soluble in water (except 
; g C0 3 in absence of NH 4 CI), whereas those of all other metals 
e but slightly or difficultly soluble. 

The estimation of potassium and sodium is required in the 
lalysis of rocks, clays, soils, ashes of plants, waters, brines, 
iline deposits, salts of the alkalies, and in many technical prod- 
sts. The determination of potassium is of special importance 
l the analysis of fertilizers. The estimation of lithium is desired 
1 the analysis of lithium minerals frequently in mineral waters, 
ccasionally in rocks, and in certain other special substances. The 
stimation of rubidium and caesium is seldom required. For the 
;ss common elements lithium, rubidium and caesium consult 
'art VI. 






142 


QUALITATIVE ANALYSIS 


Individual Characteristics. 

The common characteristics will be omitted in the following 
descriptions. 

MAGNESIUM 

Mg; at.wt. 24.32; sp.gr. 1.69-1.76; m.p. 661°; b.p. 1120° C.; oxide MgO 

Magnesium is a white metal having a lustre similar to that of metallic 
aluminum. The element decomposes hot water, forming magnesium hydrox- i$ 
ide and the liberation hydrogen. It burns at red heat with a bright whit( 
light. It will combine with nitrogen at white heat. Unlike the other mem- i 
bers, it does not oxidize in dry air. It is the hardest metal of the list, and car ffl < 
be molded, and is ductile and malleable. ^ 

Magnesium is soluble in acids and is also attacked by the acid alkali car- :r 
bonates. It is soluble in ammonium salts. The oxide, hydroxide, and theft 
salts of magnesium are soluble in acids. Combined in silicates, however, therf 
substance requires fusion with alkali carbonates to bring it into solution. q 

The insolubility of its phosphate in an alkaline solution is used for its! 
separation from the other members of the group. 

Among the less water soluble compounds are: magnesium—ammonium sul¬ 
phate, MgNH 4 P0 4 , • 6H 2 0 (0.01322) 1 ; ammonium arsenate, MgNH 4 • As0 4 • 6H 2 0 
(0.038); borate, Mg(B 0 2 ) 2 - 8 H 20 ; carbonate, MgC03(0.0106); fluoride, MgF s 
(0.0087 18 °); hydroxide, Mg(OH) 2 (0.0009); oxalate, MgC 2 0 4 -2H 2 0 (0.07 16 °); 
oxide, MgO (0.00062); phosphate, Mg3(P0 4 ) 2 -4H20 (0.0205); and pyrophos¬ 
phate, Mg 2 P 20 7 . 

DETECTION 

1 

General Procedure.—In the usual course of analysis magnesium is found 
in the filtrate from the precipitated carbonates of barium, calcium, and stron¬ 
tium. Magnesium is precipitated as white magnesium ammonium phosphate, 
MgNH 4 P0 4 , by an alkali phosphate, Na 2 HP0 4 , NaNH 4 HP0 4 , etc., in pres¬ 
ence of ammonoum chloride and free ammonia. The precipitate forms 
slowly in a dilute solution. This is hastened by agitation and by rubbing 
the sides of the beaker during the stirring with a glass rod. Crystals soon 
appear on the sides of the beaker in the path of contact, and finally in the 
solution. 

Baryta or lime water added to a solution containing magnesium produces 
a white precipitate of magnesium hydroxide. 

Both the phosphate and the hydroxide of magnesium are soluble in acids. 

1 The figures in brackets represent the grams weight of the substance 
soluble in 100 cc. of cold water. 








THE METALS 


143 


AMMONIUM 

Ammonia. NH 3 , m.w. 17.03; D. (air) 0.6971; sp.gr. liquid 0.6234; m.p. 

77.3°; b.p. —38.6° C., Crit. temp. 130°; liquid at 0° with 4.2 atmospheres 
ressure. Commercial 28 per cent NH 3 , sp.gr. 0.90. 

The gas is very soluble in water, alcohol, ether, etc. It occurs combined 
ith acids in the air, in rain water, and in mineral springs, in the soil, in 
arnallite, guano, urine, etc. It is easily formed from the animal or vegetable 
issues by bacterial decomposition. 

A large number of compounds are known, most of these are soluble in 
old water. Among the few which are not easily soluble the following are 
lore common: ammonium antimonate, NH 4 Sb0 3 -2H 2 0, bromo platinate, 
NH 4 ) 2 PtBr 6 , (0.59 20 °) red; chloroiridate, (NH 4 ) 2 IrCl 6 (0.7 14 °) reddish 
>rown; chloroplatinate, (NH 4 ) 2 PtCl6 (0.67 20 °) yellow; metavanadate, 
ttI 4 V0 3 , white, (slightly soluble in H 2 0, insoluble in presence of NH 4 C1); 
►hosphomolybdate, (NH 4 ) 3 P0 4 12Mo0 3 -3H 2 0 (0.03 15 °) yellow. The am- 
aonium radical NH 4 acts as an univalent cation combining with the acid 
adicals. 


DETECTION 

Ammonia.—Free ammonia is readily recognized by its characteristic odor, 
glass rod dipped in hydrochloric acid and held in fumes of ammonia produces 
i white cloud of ammonium chloride, NH 4 C1. 

Moist red litmus paper is turned blue by ammonia. Upon heating the 
laper the red color is restored, upon volatilization of ammonia (distinction 
:rom fixed alkalies). 

Nessler’s Test. 1 —Nessler’s reagent added to a solution containing am¬ 
monia, combined or free, produces a brown precipitate, NHg 2 I-H 2 0. If the 
ammoniacal solution is sufficiently dilute a yellow or reddish-brOwn color is 
produced, according to the amount of ammonia present. The reaction is 
used in determining ammonia in water. 

Salts of ammonia are decomposed by heating their solutions with a strong 
base such as the hydroxides of the fixed alkalies or the alkaline earths. The 
odor of ammonia may now be detected. 

1 The reagent is made by dissolving 20 grams of potassium iodide in 50 
cc. of water, adding 32 grams of mercuric iodide and diluting to 200 cc. To 
this is added a solution of potassium hydroxide—134 grams KOH per 260 
cc. H 2 0. 




144 


QUALITATIVE ANALYSIS 


POTASSIUM 

Potassium, K, at.wt. 39.10; sp.gr. 0.875; m.p. 62.6°; b.p. 757.6° C.; oxide 

K 2 0, k 2 o 4 . 

The element closely resembles sodium. It occurs as a chloride and su j 
phate in sea water and mineral springs; also in large deposits, generally 
above rock salt (Stassfurt deposits in Germany). Potassium is the mos ] 
essential and least variable of all elements found in plant ash. 

A large number of compounds are known. The salts are generally solubl 
in cold water. Among the exceptions are the following: Potassium-anti 3 
monate, KSb0 3 ; cobaltinitrite, 2Co(N0 2 ) 3 *6KN0 2 '3H 2 0 (0.09) yellow 
chloroplatinate K 2 PtClo (0.48 2 °) yellow; thioplatinate, K 2 Pt 4 S 6 ; bluisi 
gray cryst.; uranate, K 2 U0 4 , orange yellow. The presence of alcohc 
decreases the solubility of the salts. See list of compounds in Part V. 

DETECTION 

For the detection of potassium in insoluble compounds, bring the sampl, 
into solution by one of the methods given under preparation of the solutioi 
under Detection of the Metals, Part IV. In other cases, prepare a stron 
solution of the material to be tested. Where only very small amounts c 
potassium are present, remove all the constituents from the solution excep 
the chlorides of magnesium and the alkalies by precipitation as sulphides 
hydroxides and carbonates. In the presence of considerable amounts c 
potassium, small quantities of other constituents will not materially interfer 
with the flame and spectroscopic tests. After acidifying with hydrochlori 
acid, bring a drop of the solution to be tested into the non-luminou 
flame and observe the color produced through a blue color screen. In th 
presence of potassium, a distinct reddish-violet coloration will be apparent 
This must not by confused with the color caused by large amounts of sodium 
which appears bluish-violet through the screen. Comparison with the colora 
tion produced by pure salts is advisable. If necessary, confirm the result 
by examining the flame in the spectroscope. In the presence of a moderat* 
amount of a volatile potassium compound, a bright red line will be readil: 
seen in the red portion of the spectrum, and a less distinct violet line will b 
visible in the violet field, 









THE METALS 


145 


SODIUM 

)dium, Na, at.wt. 23.00; sp.gr. 0.9735; m.p. 97.6°; b.p. 877.5°C.; oxides 

Na 2 0, Na 2 0 2 . 

The metal is insoluble in kerosene and benzene. Sodium is the most 
idely distributed element of the group. It occurs as a chloride in enormous 
;posits as rock salt. It occurs in mineral water, sea water, springs, and 


Among the large number of sodium compounds a few only are difficultly 
luble in cold water. Of these the following are worthy of note: Sodium- 
ltimonate, 2NaSb0 3 -7H 2 0 (0.031 120 ); pyroantimonate, Na 2 H 2 Sb 2 0 7 *H 2 0; 
molybdate, Na 2 Mo 2 0 7 ; uranate, Na 2 U 04 , yellow. See compounds in Part V. 


DETECTION 

Sodium is usually identified by the color which it imparts to the flame or by 
leans of the spectroscope. The solution is prepared as directed under Prep- 
ration and Solution for Metals, Part IV, and is freed from all constituents 
ther than the chlorides of magnesium and the alkalies by removal of these as 
llphides, hydroxides and carbonates by the standard procedure. With 
xceedingly small amounts of sodium, it may be necessary to remove the 
lagnesium also. After acidifying with hydrochloric acid, a drop of the 
Dlution is brought into the flame by means of a loop of platinum wire. In 
he presence of sodium, the flame assumes an intense yellow color, which is 
sually sufficient to identify the element. The results may be confirmed by 
xamining the flame in the spectroscope, when the characteristic yellow 
odium line will be prominent even in the presence of traces of sodium. As 
, matter of fact, the ever-presence of the sodium line is a hindrance to the 
uccess of the method, but by observing the sudden change in the intensity 
>f the line, little trouble will be experienced in detecting exceedingly small 
mounts of the metal. 

Sodium may also be detected by precipitation as sodium pyroantimonate, 
sTa 2 H 2 Sb 2 0 7 -H 2 0, from a sufficiently concentrated neutral or weakly alkaline 
olution by means of a solution of acid potassium pyroantimonate. The 
jrecipitate comes down in granular or crystalline form, and its formation is 
lastened by rubbing the sides of the vessel with a glass rod. In making this 
,est, magnesium must be previously removed from the solution. 

In waters and soluble salts, it is usually sufficient to test directly the con¬ 
sentrated solution in the flame or spectroscope. 



146 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 


Chemical Reactions of the Soluble Basic Group 

Make the tests for the alkalies with concentrated solutions o: 
their chlorides. For the flame and spectroscopic tests use a little 
of the solid dissolved in HC1. The platinum wire should be clean 
See Introduction, also Dry Tests in Part IV. 


! 


MAGNESIUM 


Use a solution of MgCl 2 or Mg(N 03 ) 2 . 

1. Make a portion alkaline with a few drops of NH4OH anc 
add a solution of (NH^COa- The precipitate is a double sal 
of magnesium ammonium carbonate. 

Reactions.—(a) MgCl 2 +2NH 4 OH = j Mg(OH) 2 (white) +2NH 4 C1. 


(b) 4MgCl 2 +4(NH 4 ) 2 C0 3 +H 2 0= i Mg 4 (C0 3 ) 3 (0H) 2 + T C0 2 +8NH 4 C1 

2. Now add a few drops of NH4CI and heat the solution. Doei 
the precipitate dissolve? 


Reaction—Mg(OH) 2 +2NH 4 Cl+2NH 3 = Mg(NH 3 ) 4 Cl 2 (solution) +2H 2 0 


3. Try the same test, beginning with a neutral solution ir 
place of a solution made alkaline with NH4OH. 


Write out reaction. 


4. To another portion add NH 4 OH to alkalinity, and a fev 
drops of NH4CI and then 2-3 cc. of Na 2 HP0 4 solution. The 
precipitate is MgNH 4 P0 4 . Does the addition of alcohol hastei 
precipitation? Does stirring with a glass rod hasten precipitation' 

Reaction.—MgCl 2 +Na 2 HP0 4 +NH 4 0H = [ NH 4 MgP0 4 (white cryst. 

+2NaCW+H 2 0. 

Note .—Neutral solution Na 2 HP0 4 precipitates flocculent MgHP0 4 . 

Reaction.—MgCl 2 +Na 2 HP0 4 =i MgHP0 4 (white flocc.)+2NaCl. 






THE METALS 


147 


5. Add to another portion Ba(OH) 2 . The white precipitate 
Mg(OH) 2 . 

Reaction.—MgCl 2 +Ba(OH ) 2 = | Mg(OH) 2 +BaCl 2 . 

AMMONIA 

6. In analysis, the original substance or solution is used. For 
le preliminary test use either solid NH 4 C1 or its solution. (Any 
mmonium salt will do.) Place in a test tube and pour on material 
-3 cc. of NaOH and warm. An odor of ammonia can readily 
e detected. Moist red litmus paper held over the mouth of 
le tube will be turned blue. Care should be taken not to con- 
iminate the sides of the tube with the strong base. If the change 
f color is due to ammonia, the red color can be restored by heating 
le paper to drive off ammonia. 

7. Precipitation test with H 2 PtCl 6 . Chloroplatinic acid pre- 
ipitates a yellow crystalline compound (NH 4 ) 2 PtCl 6 . The salt 
j similar to that of potassium, from which it may be distinguished 
y heating with NaOH, the odor of NH 3 becoming evident. 

8. Cobaltinitrite produces a yellowish precipitate with con- 
entrated solutions of ammonium salts, similar to the potassium 
alt formed by this reagent. 

POTASSIUM 

Use a concentrated solution of KC1. 

9. To about 5 cc. add 2-3 drops of acetic acid, and then an 
qual volume of sodium cobaltinitrite. If no precipitate forms 
mmediately, allow to stand 15 or 20 minutes. A yellow pre- 
ipitate is KaCo(N0 2 )6+water of crystallization. 

Note .—The test cannot be applied in the presence of ammonium salts, 
ince NH 4 yields a similar precipitate. 

10. H 2 PtCl6 precipitates yellow, K 2 PtCl6 from neutral solu- 
ions, or concentrated acid solutions of potassium salts. See 
imilar test for ammonia. 




148 


QUALITATIVE ANALYSIS 


Compare solubilities of the potassium cobaltinitrite and chloroplatim 
salts. It is evident that precipitation in the first form is a more sensiti 
test for potassium. See list of compounds in Part V. 

11. Make the flame test with a small amount of the salt. E 
amine through the same thickness of blue glass used in t 
sodium test. What advantage can be taken of this test? 

SODIUM 

Use a concentrated solution of NaCl. 

12. To a portion placed in a test tube, the solution being ne 
tral or slightly alkaline, add an equal volume of dipotassiu 
dihydrogen pyroantimonate (K 2 H 2 Sb 20 ?), shake vigorously ai 
allow to stand some time. The white crystalline precipitate 
Na 2 H2Sb207H 2 0. 

Note .—The solution must not be acid, as this would decompose the reage: 
causing the precipitation of pyroantimonic acid. 

Reactions.—(a) 2NaCl+K 2 H 2 Sb 2 0; =1 Na 2 H 2 Sb 2 0 7 (white)+2KC1. 

(6) Acid on reagent—K 2 H 2 Sb 2 0 7 -f-2HCl = | H 4 Sb 2 0 7 (white) +2KC1. 

Removal of other metals (except NH 4 and K) is necessary, since tb 
yield precipitates with the reagent. 

13. Make a flame test with a portion of the solution or i 
the solid salt with a few drops of HC1. Now examine the flai 
through a blue glass. If the glass is of proper density, the yelh 
rays will be entirely absorbed. Several thicknesses of glass m 
be necessary to cut out the rays. 

14. Examine the spectrum of sodium. 

For the less common elements, lithium, caesium, rubidium, t 
Part VI. 


THE METALS 


149 


utline of the Method for Detecting the Soluble Group Metals 

Direct tests may be made for members of this group in presence 

one another so that it is not necessary to effect a complete 
paration as in case of previous groups. Since Na 2 HP 04 pre- 
pitates the alkaline earth metals the removal of these is necessary 
r a reliable test for magnesium, since the carbonates of Ba, Ca 
id Sr are slightly soluble and small amounts pass into the filtrate 
>ntaining the soluble group. This removal is accomplished 
1 one-third portion of the solution by adding (NH 4 ) 2 C 2 C >4 and 
^H4)2S04, boiling and filtrating off the precipitated alkaline 
trths. The concentrated filtrate is tested for magnesium. The 
maining two-thirds of the original solution is evaporated to 
•yness and heated to expel the accumulated ammonium salts, 
hich interfere in the detection of potassium on account of the 
Imilarity of ammonium compounds that would form with 
agents used. These salts are volatilized at a temperature 
here practically no loss by volatilization of the alkalies occurs, 
ests for sodium and potassium are made in separate portions. 

Ammonia is looked for in the original sample for the obvious 
sason that reagents containing this compound are used in the 
)urse of analysis. 



150 


QUALITATIVE ANALYSIS 


Analysis of the Soluble Basic Group 

Preparation of Solution 

Divide the filtrate from the Ammonium Carbonate Group into two p( 
tions: A, one-third, and B, two-thirds. Test portion A for magnesium, ai 
meantime evaporate portion B to small bulk on a sand bath and finally 
dryness on a water bath, and proceed as indicated in B , below. 

Removal of the Alkaline Earth Metals 

A. Before proceeding to the test for magnesium, traces of the previc 
group must be removed from the solution. In order to detect the preser 
of these add a few drops of the solution to about 2-5 cc. of a strong soluti 
of (NH 4 ) 2 S 04 ; a slight turbidity indicates the presence of strontium 
barium or both. To detect the presence of calcium add one or two cc. of t 
solution to an equal volume of (NH 4 ) 2 C 2 0 4 ; a slight turbidity is due to t 
formation of CaC 2 0 4 . If the tests indicate Sr, Ba, or Ca, add to the remainc 
of the portion A the reagents effecting their precipitation, and filter. 

Detection of Magnesium 

Residue.—Reject. Solution contains magnesium and the alkalies. C( 
centrate the solution to about 5 cc. (Filter off any precipitate that may forr 
To the filtrate add 1-5 cc. (NH 4 ) 2 HP0 4 solution and stir with a glass re 
A white, crystalline precipitate forming slowly, crystallizing in streaks where’i 
the rod has touched the beaker, proves the presence of Magnesium. (T 
solution should be made alkaline with NH 4 OH before the addition 
(NH 4 ) 2 HP0 4 , if not already so.) 

Confirmation of MgNH 4 P0 4 .—Dissolve the precipitate in a little ace 
acid. To the clear filtrate add NH 4 OH to make the solution alkaline. S 
vigorously and allow to stand. MgNH 4 P0 4 is again precipitated. 

Separation of the Alkalies—Potassium, Sodium and Lithium 

B. (a) Procedure in Presence of Magnesium and the Alkaline Earths .—■' 
remove magnesium expel the ammonium salts by heating the residue obtain< 
by evaporation, to a temperature below dull redness until no more white fun 
are driven off. (Hood.) Heat the sides of the dish as well as the botto 
Dissolve the residue in about 5 cc. of water and add Ba(OH) 2 , drop by dr< 
until no further precipitation occurs. The precipitate is Mg(OH) 2 . Filt 
rejecting the residue. To the filtrate add a few drops of (NH 4 ) 2 S0 4 to remc 


THE METALS 151 

rium. When the precipitation is complete add several drops of (NH 4 ) 2 C 2 O 4 
i filter. Reject the precipitate. (Ba, Sr, Ca.) Evaporate the solution 
dryness, 

(6) Procedure after the Removal of Magnesium and the Alkaline Earths.— Expel 
5 ammonium salts by heating in a hood to a temperature below dull redness 
til no more white fumes are driven off. (Heat sides as well as the bottom 
the dish.) Add about 10 cc. of water containing a few drops of HC1 (1.12), 
,rm and filter, and again evaporate the filtrate to dryness. Take up the 
sidue with 5-10 cc. of water. Filter if not clear. Divide into two portions, 
md II. 


Portion I.—Add a few drops of 
etic acid if the solution is not 
*eady acid, and an equal volume of 
a 3 Co(N0 2 )6. Allow to stand 10 to 
minutes if a precipitate does not 
rm readily. A yellow precipitate is 
3 Co(N0 2 )6+aq., best seen on filter 
tper upon removal of the reagent 
t washing. Filter and wash residue 
ith water, a few drops at a time. 
Potassium may also be detected by 
•ecipitation as K 2 PtCl6. See Chemi- 
d Reactions, page 147. 

Confirm.—Dissolve residue in a 
:tle hot HC1 (1.12). Evaporate to a 
w drops and test the concentrated 
•lution in the flame, cutting out the 
3 II 0 W rays by blue glass of sufficient 
ansity. A violet red color indicates 
atassium. Examine by spectro- 
:ope. A flame violet-red giving a 
*d and a blue line proves Potassium. 


Portion II.—If the solution reacts 
acid, make neutral by the addition of 
a drop or so of KOH. Evaporate to 
about 1 cc., cool, and add 1 to 2 cc. 
K 2 II 2 Sb 2 0 7 ; pour into a test tube and 
allow to stand for some time (at least 
half an hour or longer). A white crys¬ 
talline precipitate is Na 2 H 2 Sb 2 C>7H 2 0. 

Confirm.—Decant off the solution. 
Wash the precipitate by adding small 
amounts of water at a time Test the 
residue in the flame, upon the addition 
of a drop or so of HC1 to bring it into 
solution. A brilliant yellow flame 
proves the presence of Sodium. Ex¬ 
amine the flame by means of the spec¬ 
troscope to detect the presence of 
Lithium. 


Ammonium.—Test original substance or solution by warming with a little 
aOH. Odor of ammonia. See tests for ammonia under the characteristic 
jsts. 

Moist red litmus paper is colored blue by NH 3 . In warming the paper 
le NH 3 is volatilized and the red color restored. (Distinction from the other 
ikalies.) 






152 


QUALITATIVE ANALYSIS 


Notes on the Analysis of the Soluble Basic Group 

Test for Magnesium.—Since the phosphates of the alkaline earths are i 
insoluble in alkaline solutions, calcium, barium, and strontium must 1 
removed completely from the solution before making the test for magnesiur 

Evaporation.—Ammonium salts must be expelled, since they show tl 
same reaction as potassium. The residue is not heated to redness, as the alk* 
chlorides will volatilize when highly heated. 

Precipitation. —The residue obtained upon the expulsion of the ammoniu 
salts may be tested directly by flame and spectroscopic tests by dissolving it 
a few drops of HC1. The difficulty lies principally in the detection of potassiu 
in the presence of sodium. A blue glass of sufficient density to cut out tl 
yellow rays of sodium should be used. Again the fact that sodium is alwa; 
present in the reagents and in the air makes the direct flame test unsatisfactor 
as a yellow color will always be obtained with the residue, hence the advi 
ability of using the precipitation test, since these traces will not respond 
this test. For satisfactory results great care must be used. 

In the precipitation of potassium by cobalt nitric solution, if an excess 
sodium is present, the potassium comes down as K 2 NaCo(N 02 VH 20 . 

Reagents. Sodium Cobaltinitrite. —Dissolve 100 grams of NaN0 2 in 200 c 
of water, add 60 cc. acetic acid (30 per cent) and 10 grams of Co(N0 3 )2-6H 2 < 
Allow to stand for two or three days; filter and dilute to 400 cc. 

Dipotassium Dihydrogen Pyroantimonate. —Dissolve 2 grams of the be 
commercial salt, K 2 H 2 Sb 207 ,in 100 cc. of boiling water and boil the solution f 
about a minute, cool quickly and add 3 cc. KOH (10 per cent) and filter. 

Test for Potassium. —The solution must not be alkaline when the reagent 
added, since Co(OH) 3 would precipitate as soon as Na 3 Co(N0 2 )6 is added 
alklaine solutions, hence the addition of acetic acid. 

Test for Sodium is made from neutral solutions, as Na 2 H 2 Sb 207 is soluble 
an acid solution. The salt is a heavy crystalline precipitate, which im 
require some time for complete precipitation. The precipitate due to tl 
presence of lithium is similar to that of sodium. The flame and spectroscop 
tests serve as a ready method of distinction, since lithium gives a carmine-r< 
flame, and has in its spectrum a red and a feeble orange line. A fleeti] 
yellow color should not be taken as evidence of the presence of sodium. 

For a method of determination of lithium the student is referred to a pap 
by W. C. Bray, The Journal of the American Chemical Society , June, 190 
His method is to precipitate lithium as a phosphate from an alcoholic solutic 
containing the alkalies. 

Test for Ammonia is made with the original solution or solid, since durii 
the process of analysis this substance has been added as a reagent in both tl 



THE METALS 


153 


mmonium Sulphide and Ammonium Carbonate Groups. It is not necessary 
dissolve the sample, as the test may be made of the solid substance. 

CLASSROOM EXERCISES 

| ' 

1. What substances are present in an ionized solution of NH 4 OH, NaCl, 
'OH? The student must remember that complete ionization does not take 
lace. (See Introduction.) 

2. What impurities are found in common salt? How is it purified? 

3. What metal is removed from the other members of the group by 
recipitation? 

4. Why is it necessary to test for ammonia in the original sample? 

5. What precautions are observed in testing for magnesium? 

6. Why is it necessary to remove ammonia before testing for potassium? 

7. What metals have been examined by means of the spectroscope? 
7hat elements have been discovered by this means? 

8. Write out all reactions involved in the analysis of the members of this 
roup. 


GENERAL REVIEW OF THE METALS 

1. Study the table outlining the procedure for separation of the basic 
lements given on page 230. 

2. Outline the procedure for separation and detection of silver, copper, 
in, zinc and magnesium in a mixture of their chlorides. 

3. A white compound is given for analysis. This is insoluble in cold water, 
3 ut goes into solution when heated. On cooling, crystals are formed. K 2 Cr0 4 
idded produces a yellow precipitate—what is the compound? 

4. Review the tables of reactions in Part V. 

5. How would you distinguish between: 

(a) Antimony and arsenic in a mixture of the two? 

(b) Antimony and bismuth chlorides? 

(c) Ferrous and ferric iron? 

(d) Lead sulphate and barium sulphate? 

(e) Copper chloride and nickel chloride? 

(/) Chromic salt and a soluble chromate? 

(g) Magnesium chloride and zinc chloride? 


PART III 


THE ACIDS 


General Characteristics. 

Acids are electrolytes containing the common cation H + , whic 
may be replaced by metals, forming salts. The chemical activit 
of acids depends upon their degree of ionization. Analysis of acic 
is the identification of the negative ion or the anion. This can fc 
accomplished by testing directly for the radical. Although it i 
impossible to analyze acids by a process of elimination such as wa 
used in the case with the metals, yet, by means of certain genen 
tests or preliminary reactions, it is possible to recognize manyc 
the acids, which can be further confirmed by special tests. Only 
few anions need be looked for in an ordinary analysis, since th 
presence of certain metals in the solution proves the absence c 
certain acids. For example, if silver has been found in a solutio 
soluble in water, chloride, bromide, and iodide anions are absenl 
since they would combine with silver to form insoluble salts; like 
wise, a sulphate cannot be found in a water solution containin 
barium or lead, nor an oxalate in a neutral solution containin 
calcium. Furthermore the presence of certain metals furnishes 
clue to the presence of certain acid radicals, generally associate' 
with these metals. The tests for acids, therefore, follows th 
analysis of the metals. 

Classification. 

Acids may be classed under two major heads—Inorganic an< 
Organic. The latter includes a very large number of acids, only 
few of which concern us in our present course. The general chai 
acteristic of organic acids is their readiness to decompose whe] 
heated, leaving a black residue of carbon (charring). 

154 


THE ACIDS 


155 


Acids are frequently classed under three general groups, based 
l the solubility of their salts. A number, for example, form in- 
luble salts in an acid solution with silver nitrate, others form 
soluble salts in a neutral solution with barium chloride, and a 
ird class remains in solution in the presence of either or both 

these reagents. The fact that certain acids volatilize or decom- 
)se under the influence of free dilute acids, such as nitric, hydro- 
lloric, or sulphuric, and the organic acids char when heated, 
is led us to include two additional groups as a matter of conveni- 
lce in our study of the individual properties and special tests 
[ the acids. 

The members of these jive groups will be taken up in the order 
iven in the following table. Since the alakli salts of many of the 
dds ionize readily and are soluble , it is advisable to use these in 
le special tests for the acids. 

I. The Volatile Acid Group. —Acids volatilized or decomposed 
/hen their salts are acted on by dilute nitric, hydrochloric, or sul- 
ihuric acids. 

H 2 CO 3 , (HCN included in II), HCIO, HN0 3 , H 3 SiO a (precipitated), 

I 3 S, H 3 S0 3 , h 3 s 3 o 3 . 

II. The Silver Nitrate Group. —Acids whose silver salts are 
nsoluble in solutions acidified with dilute nitric acid. 

The following acids are precipitated by AgNC>3 in dilute 

TN0 3 . 

HC1, HBr, HI, HCN, H 4 Fe(CN) 8 , H 3 Fe(CN) 6 , HSCN. 

III. The Barium Chloride Group.— Acids whose barium salts 
ire insoluble in water. 

The group is subdivided into two parts: (a) Acids whose 
barium salts are insoluble in dilute acids. The acids precipitated 
by BaCl2 in dilute acid solutions are: H 2 SO 4 , HF. 

( b ) Acids whose barium salts are soluble in dilute acids. The 
acids precipitated by BaCb in neutral solutions are: 



156 


QUALITATIVE ANALYSIS 


HjPO<, H 3 AsOj, H 3 As0 4 , H3BO1, H 2 Cr0 4 , (H 2 COj, HjSiOj, HjSjOj 
IlaSiO*, HaCa0 4 , H 2 C 4 H 4 0 6 included in I and V). 

IV. The Soluble Acid Group. —Acids whose barium and silve; 
salts are soluble in water. 

The following acids belong to this group: 

HNO 3 (HNOa included in Group I), HC10 3 , HMn0 4 (HC 2 H 3 0 a includec 
in Group V). 

V. Organic Acids. —Under this head will be considered: 

(a) Acids which char on heating HC2H3O2, H2C4H4O6. 

( b ) Acids which do not char on heating: H2C2O4, H2C7H4O3 


THE VOLATILE ACID GROUP 

DESCRIPTIVE 

general Characteristics. 

The acids of this group are volatilized or decomposed when their 
salts are treated with dilute nitric, hydrochloric, or sulphuric acid. 

Individual Characteristics. 

CARBON AND ITS ACID COMBINATIONS 

C, at.wt. 12.0; sp.gr. amorp. 1.75-2.10; cryst.; graphite, 2.25; diamond, 
3.47-3.5585; m.p. sublimes at 3500° C.; oxides, CO and CO a . 

The element occurs free in nature in the crystalline forms, diamond and 
graphite, and in the amorphous form, charcoal, coke, etc. It occurs in iron, 
steel, and in certain alloys. 

Combined as a carbonate it occurs in a large number of substances, among 
which are found calcite, marble, limestone, dolomite, magnesite, strontianite, 
witherite, spatic iron ore. It occurs as the dioxide in the air in water 
(HjO COj) and in flue gas. Carbon dioxide is the active constituent of 
baking powders (NaHCOj). 

Carbonic Acid, H 2 C0 3 , Carbonate.—Like sulphurous acid, carbonic 
acid has never been isolated. The anhydride CO 2 mol.wt. 44; sp.gr. 
(A) 1.53; m.p.-65°; b.p.-78.2°. 

Carbon dioxide is a colorless, odorless gas, easily freed from its salts by 
many mineral acids. Since it is but slightly dissociated, it is a feeble acid, 
hence its normal salts are alkaline in reaction. The normal carbonates, 
except those of the alkalies, are insoluble in water; many, however,' are 
soluble in excess of C0 2 , forming soluble bicarbonates. All carbonates are 
decomposed by heat except carbonates of the alkalies and BaC0 3 . Nearly all 
carbonate salts are white. 

DETECTION 

Element.—Carbon is recognized by its appearance and by its inertness 
towards general reagents. It is seen in the charring of organic matter when 
heated or when acted upon by hot concentrated sulphuric acid. 

Upon combustion with oxygen or by oxidation with chromic and sulphuric 
acids, carbon dioxide is formed. 


157 





158 


QUALITATIVE ANALYSIS 


Carbon Dioxide.—The gas passed into lime water forms a white precipi¬ 
tate, CaC0 3 . White precipitates are formed when the gas is led into baryta 
water (BaC0 3 ppt.), or into an ammoniacal solution of lead 
acetate (PbC0 3 pptd.). 

Carbonate.—Action of mineral acids causes effervescence, 
C0 2 being evolved. The gas is odorless (distinction from S0 2 , 
H 2 S, and N 2 0 3 ) and is colorless (distinction from N 2 0 3 ). The 
gas absorbed in the reagents above mentioned produces a 
white precipitate. The test is best made by placing the 
powdered material in a large test tube with a stopper carrying 
a funnel and delivery tube as shown in the illustration, Fig. 13. 
For small amounts of combined C0 2 , warming of the test tube 
may be necessary. Sulphuric or phosphoric acid should be 
used to liberate the gas, which is conducted into the reagent 
used for the test. 

Distinction between Soluble Carbonate and Bicarbonate. 

—The solution of the former is alkaline to phenolphthalein 
indicator (pink). Bicarbonate solutions remain colorless with 
this indicator. Normal carbonates precipitate magnesium 
carbonate when added to magnesium sulphate solution; bicarbonates cause 
no precipitation. 

Carbon Monoxide. The gas burns with a violet colored flame and is not 
absorbed by potassium hydroxide or lime water (distinction from C0 2 ). It is 
oxidized to C0 3 and so detected. With hot, concentrated potassium hydrox¬ 
ide potassium formate is produced. 

The gas is detected in the blood by means of the absorption spectrum. 



THE VOLATILE ACIDS OF CHLORINE 
See Silver Nitrate Group for the Element and its other acid combinations. 


Hypochlorous Acid, HCIO, and Hypochlorite 

Among the oxygen acids of chlorine we find: hypochlorous acid, HCIO, 
chlorous acid, HC10 2 , chloric acid, HC10 3 , and perchloric acid, HC10 4 . The 
first of these, hypochlorous acid, is important on account of the use of its 
salts in commerce as bleaching agents. Hypochlorous acid has not been 
isolated. It is a very weak acid and is easily driven from its salts by other 
weak mineral acids. Decomposition takes place at once, chlorine water and 
oxygen being formed. The hypochlorites are consequently strong oxidizing 









THE ACIDS 


159 


agents. When a solution of an alkali hypochlorite is boiled it is converted 
into a chloride and a chlorate. 

DETECTION 

Test for Hypochlorite.—Potassium hypochlorite, KCIO, shaken with 
mercury forms the yellowish red compound Hg 2 OCl 2 , which does not 
form with the other potassium salts of chlorine, i.e., KC1, KC10 2 , KC10 3 , 
KC10 4 . 

Hypochlorites decolorize indigo, but do not decolorize potassium perman- 
: ganate solutions. If arsenous acid is present, indigo is not decolorized until 
all of the arsenous acid has been oxidized to the arsenic form. 

Tests for Chlorites.—Potassium permanganate solution is decolorized by 
chlorites. (The solution should be dilute.) 

A solution of indigo is decolorized, even in presence of arsenous acid 
I (distinction from hypochlorites). 


NITROUS ACID, HN0 2 , AND NITRITES 1 

HN0 2 occurs as ammonium nitrite to a small extent in the air, in rain 
water, and in mineral springs. It occurs as nitrites in many plant juices 
and in animal mucus. Most of the nitrites dissolve readily in water. The 
silver salt is sparingly soluble. 


DETECTION 

Dilute sulphuric acid or acetic acid added to a nitrite decomposes the salt 
with evolution of nitric oxide, NO, which immediately oxidizes in the air, 
forming the brown nitrogen peroxide gas, N0 2 . Nitric oxide has a bleaching 
action on potassium permanganate. 

Acetic Acid Test.—Acetic acid added to a nitrite in a test tube (inclined 
as directed in the nitric acid test on pages 201, 203), produces a brown 
ring. Nitrates do not give this. If potassium iodide is present in the solu¬ 
tion, free iodine is liberated. The free iodine is absorbed by chloroform, car¬ 
bon tetrachloride or disulphide, these reagents being colored pink. Starch 
solution is colored blue. 

Nitrous acid reduces iodic acid to iodine. The iodine is then detected 
with starch, or by carbon disulphide, or carbon tetrachloride, or chloroform. 

Potassium Permanganate Test.—A solution of the reagent acidified with 

1 See nitrogen and its acid combinations, under the Soluble Acid Group, 
for other acids of nitrogen. 



160 


QUALITATIVE ANALYSIS 


sulphuric acid is decolorized by nitrous acid or nitrite. The test serves to 
detect nitrous acid in nitric acid. Other reducing substances must be absent. 
See tests under Laboratory Exercises, page 165. 

SILICON AND ITS ACID COMBINATIONS 


Si, at.wt. 28.3; sp.gr. amor. 2.00; crys. 2.49; m.p. 1420° C.; 


oxides SiO, Si0 2 


The element silicon has no important application. Its use for electrical 
resistance has been suggested. A rod 10 cm. long with cross-section of 40 
sq.mm, has a resistance of 200 ohms against a carbon rod of the same dimen¬ 
sions of 0.15 ohm. Impure silica finds use in fluxes in manufacture of glass, 
pure silica for the manufacture of silica ware. With caustic it forms an 
adherent sodium silicate. Silicon carbide, carborundum, is used for refractory 
purposes, fire brick, zinc muffles, coke ovens. Crystolon, the crystalline 
form, is used as an abrasive, in making grinding wheels, sharpening stones, etc. 

Combined as Si0 2 and in silicates the element is very widely distributed in 
nature and is a required constituent in practically every complete analysis of 
ores, minerals, soils, etc. It is present in certain alloys, ferro-silicon, silicon 
carbide, etc. 

The element is scarcely attacked by single acids, but is acted upon by 
nitric-hydrofluoric acid mixture. It dissolves in strong alkali solutions. 
Silica is decomposed by hydrofluoric acid and by fusion with the fixed alkali 
carbonates or hydroxides. 


Silicic Acids, Meta, H 2 Si0 3 and Ortho, H 4 Si0 4 . Silicate 

H 2 Si0 3 —mol.wt. 78.32; sp.gr. 1.81.- Insol. in cold H 2 0, sol. in alk. 

H 4 Si0 4 —mol.wt. 96.33; sp.gr. 1.57. Slightly sol. in H 2 0, sol. in alk. 

Si0 2 —mol.wt. 60.3; sp.gr. 2.2-2.6; m.p. 1600-1750°. 

Orthosilicic, metasilicic, and the polysilicic acids all yield Si0 2 on heating. 
The silicates of nature are nearly all derived from the polysilicic acids. 

Silicic acid, H 2 Si0 3 , is one of the weakest of the mineral acids, being 
scarcely ionized at all in solution. The silicates of the alkalies are soluble 
in water. Silicates are transposed by boiling with Na 2 C0 3 . 

General Considerations.—The natural and artifically prepared silicates 
may be grouped under two classes: 1. Those which are decomposed by acids. 
2. Silicates not decomposed by acids. The minerals datolite, natrolite, 
olivine and many basic slags are representative of the first class, and feldspar, 
orthoclase, pumice and serpentine are representative of silicates not decom¬ 
posed by acids. 




THE ACIDS 


161 




t, 


DETECTION 


Fig. 14. 


The finely ground sample together with a small quantity of powdered 
calcium fluoride is placed in a small lead cup 1 cm. in diameter and depth 
(see Fig. 14) and a few drops of concentrated sulphuric acid added. A lead 
cover, with a small aperture, is placed on the cup, and 
the opening covered with a piece of moistened black 
filter paper. Upon this paper is placed a moistened 
pad of ordinary filter paper. The cup is now gently 
heated on the steam bath. At the end of about ten 
minutes, a white deposit will be found on the under 
side of the black paper, at the opening in the cover, if 
an appreciable amount of silica is present in the ma¬ 
terial tested. 

A silicate, fused with sodium carbonate or bicarbonate in a platinum dish 
and the carbonate decomposed by addition of hydrochloric acid with subse¬ 
quent evaporation to dryness, will liberate silicon as silicic anhydride, Si 0 2 . 
The silica placed in a platinum dish is volatilized by addition of hydrofluoric 
acid, the gaseous silicon fluoride being formed. A drop of water placed in a 
platinum loop, held in the flames of SiF 4 , will become cloudy owing to the 
formation of gelatinous silicic acid and fluosilicic acid. 

3SiF 4 +3H 2 0 = H 2 SiO 3 +2H 2 SiF 6 . 

If a silicate is fused in a platinum loop with microcosmic salt, the silica 
floats around in the bead, producing an opaque bead with weblike structure 
upon cooling. 


SULPHUR AND ITS VOLATILE ACID COMBINATIONS 

S, at.wt. 32.07; sp.gr. 2.035; m.p. 111°; b.p. 444.53°; oxides S 2 0 3 , S0 2 , 
SO 3 , S 2 0 7 ; principal acids, H 2 S 2 0 4 , H 2 S0 3 , H 2 S0 4 , H 2 S 2 0 3 , and H 2 S 2 O g 

Physical properties and chemical reactions are given under Detection. 
The determination of sulphur may be required in a great variety of sub¬ 
stances, mineral, rocks, sulphur ores, acids, salts, water, gas, coal and other 
organic matter. 

The substance occurs in nature principally in the following forms: 

Element.—Found free, generally mixed with earthy matter. The com¬ 
mercial product is exceedingly pure and may contain over 99.5 per cent S. 
Sulphur Dioxide.—The gas, together with free sulphur, is found in volcanic 

regions. ' , . • . , 

Hydrogen Sulphide.—Occurs in mineral waters and in the air, from 

decaying organic matter. 














162 


QUALITATIVE ANALYSIS 


Sulphide Ores.—Iron pyrite, FeS 2 (30 to 50 per cent S); pyrrhotite, 
Fe 7 S 8 ; copper pyrites, CuFeS 2 ; realgar, As 2 S 2 ; orpiment, As 2 S 3 ; galena, 
PbS; cinnabar, HgS; zinc blende, ZnS, are the principal ores. 

Sulphate Ores.—Gypsum, CaS0 4 -2H 2 0, Epsom salts, MgS0 4 -7H 2 0; 
Glauber salt, Na 2 S0 4 * 10H 2 O, are the more important sulphates. 

The following facts regarding solubility of sulphur and its combination 
should be kept in mind. 

Element.—The crystalline forms are soluble in CS 2 , the monoclinic form 
is soluble also in alcohol, chloroform and benzol. Yellow amorphous and 
plastic sulphur are insoluble in CS 2 . Sulphur precipitated by the action of 
HC1 upon (NH 4 ) 2 S x is soluble in benzol. The element is soluble in hot 
hydrates of sodium, potassium, barium and calcium, forming polysulphides 
and thiosulphates. 

Sulphide. Sulphides of Na, K, Cs, Rb, Ca, Sr, Ba, Mg, Mn, Fe are 
soluble in dilute mineral acids. The sulphides of Ag, Hg, Pb, Cu, Bi, Cd, 
Co, Ni require strong acids for decomposition. These are also insoluble in 
sodium hydroxide and potassium hydroxide solutions. As, Sb and Sn sul¬ 
phides are insoluble in dilute acids, but soluble in alkalies. 

Sulphate.—With exception of BaS0 4 , CaS0 4 , SrSO, and PbS0 4 , sulphates 
are soluble in water. 


Thiosulphate.—Nearly all are soluble in water. 


Sulphite.—With exception of the sulphites of the alkalies, sulphites of the 
metals are difficultly soluble in water, but readily decomposed by acids 
Hydrogen Sulphide, H 2 S, and Sulphide. H 2 S.—Mol.wt. 34.09- sp.gr (A) 
1.189; mp. —85.5°; b.p. —61.8°. Colorless, poisonous gas having the 
disagreeable odor of rotten eggs, burns with blue flame, forming S0 2 +H 2 0 
Easily displaced by mineral acids, from many of its salts, e.g., sulphides of the 
alkalies, alkaline earths, Mg, Mn, Zn, Fe, less easily from those of Pb, Bi, 
Cd, Sn, Sb, Co, and Ni. Most sulphides are oxidized by cone. HN0 3 or 
Aqua regia, free sulphur being liberated. 


Sulphurous Acid, H 2 SO s , and Sulphite.-Among the oxygen acids of 
sulphur, sulphurous acid and thiosulphuric acid are taken up at this point 

fr ° m thek salts mineral a ^ds such as 

HC1, HN0 3 , H 2 S0 4 , the S0 2 gas being liberated. 


Sulphurous acid has never beenisolated. Itis easily oxidized to sulphuric acid 
by oxidizing agents such as bromine water,etc. It forms normal and acid salts 
S0 2 the Anhydride.—Mol.wt. 64.07; sp.gr. (A.) 2.26; mp—76 1°* 


Sulphites of the alkalies are deliquescent and are the only sulphites that 
are easily soluble in water. They are readily transposed by boiling with 
water solution of Na 2 C0 3 . 

Thiosulphates are almost all readily soluble in water. 


THE ACIDS 


163 


DETECTION 

The following tests include the detection of free sulphur and its more 
important combined forms. 

Element.—Sulphur is a polymorphous, yellow, brittle, odorless and taste¬ 
less solid; existing in the rhombic, monoclinic and triclinic crystalline forms, 
and also in an amorphous state. At 111° it melts to a pale yellow liquid; 
at 180° it thickens to a dark gum-like material, containing a large percentage 
of amorphous sulphur; at 260° it becomes a liquid again, and at 444.53° 
it boils, giving off a brownish-red vapor. 

Heated in the air sulphur burns with a blue flame, and is oxidized to S0 2 , a 
gas with a characteristic pungent odor. This gas passed into a solution of 
potassium permanganate will decolorize it, if S0 2 is in excess of the amount 
that will react with the KMn0 4 in the solution. 

If sulphur is dissolved in a hot alkali solution and a drop of this then placed 
on a silver coin, a stain of black Ag 2 S will be evident, due to the action of the 

sulphur. . 

Sulphide.— Hydrogen sulphide, H 2 S, is liberated when a sulphide is 
treated with a mineral acid. This gas blackens moist lead acetate paper. 
HiS has a very disagreeable odor, which is characteristic. 

Sulphite.— Sulphur dioxide, S0 2 , is evolved when a sulphite is treated 
with hydrochloric acid. The odor of the gas is characteristic. 

Sulphur dioxide decolorizes a solution of potassium permanganate. (Use 
very dilute solution.) 

Sulphites are distinguished from sulphates by their failure to form a white 
precipitate, when barium chloride is added to the solution acidified with 
hydrochloric acid; also by the fact that H 2 S is formed when zinc is added to a 
solution of a sulphite, acidified by hydrochloric acid. 

Thiosulphate.— Sulphur dioxide is evolved and free sulphur precipitated 
when a thiosulphate is acidified with dilute mineral acids. In presence of 
oxidizing agents sulphides will also liberate free sulphur. 

Thiosulphates are strong reducing agents. 

Sulphur Dioxide.— Odor, etc.—SO* is evolved when a sulphite is acidified. 
This may be recognized by its odor. It is a strong reducing agent (see above). 
If passed into a solution of KMn0 4 , it will decolorize it. It is easily oxidized 
to the sulphate form by oxidizing agents such as bromine water. (See separa¬ 
tion of sulphites and sulphates at the close of the tests of this group.) Thio¬ 
sulphates liberate S as well as S0 2 ; sulphites liberate only S0 2 . 

Detection of sulphuric acid and sulphates is given under the Barium 
Chloride Group, pages 191, 197. 



164 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 
CARBONATE, C0 3 — 

1. Lime Water Test for CO 2 .—CO 2 is liberated with efferves¬ 
cence when a carbonate is acidified with a dilute mineral acid. 

Add a few drops of HC1 to a carbonate solution or salt in solid 
form. A sudden effervescence occurs. Test the gas with a drop 
of Ca(OH )2 solution on a glass rod or loop tube. A clouding of 
the lime water indicates a carbonate. (CaCC >3 formed.) 

Note .—A loop tube is made by bending a capillary glass tube at one end 
into a small loop as in case of platinum wire for borax bead tests. 

Reactions—CaC0 3 +2HCl=CaCl 2 + T C0 2 +H 2 0 
Ca(0H) 2 +C0 2 = | CaC0 3 +H 2 0. 

Precaution .—The test will fail if the lime water has been contaminated 
by HC1. An excess of C0 2 will redissolve the insoluble CaC0 3 due to the 
formation of the soluble bicarbonate, Ca(HC0 3 ) , hence the film should be 
examined shortly after exposing it to C0 2 . 

Reactions.—CaC0 3 +H 2 CO s = Ca(HC0 3 ) 2 solution. 

Ca(HC0 3 ) 2 sol. boiled = | CaC0 3 -f- T C0 2 +H 2 0. 

2. Precipitation from Solution.—BaCl 2 , CaCl 2 , AgN0 3 solu¬ 
tions each precipitate a white compound, BaC0 3 , CaC0 3 or 
Ag 2 C0 3 respectively, when added to neutral solutions of car¬ 
bonates. The precipitates dissolve in acids with evolution of 
CO 2 . Use Na2C0 3 solution for the tests. Write out the reactions. 

The student is referred to the descriptive section for detection of carbon 
and its acid combinations for further information on tests. See page 157. 

CYANIDE, CN~ 

1. HCN is liberated by action in an acid on a cyanide. (Hood.) 
The gas is a deadly poison. Tests for cyanides should be made 
according to directions under the Silver Nitrate Group, page 178. 


THE ACIDS 


165 


HYPOCHLORITE, C10“ 

1. Decomposition. —Acidify the solution or solid with dilute 
Cl; the hypochlorite will be decomposed, liberating free chlorine, 
Inch is recognized by its pungent odor and yellow color. A 
ass rod with a drop of AgNC >3 is coated with a white deposit, 
gCl. Chlorine fumes with NH 3 , forming NH4CI, a white solid. 

4KC10+4HC1 = 4KC1+ T2Cl 2 +0 2 +2H 2 0. 

2 Ca (Cl) 2 + 2 H 2 CO 3 = 2 CaCO 3 + T 2Cl 2 +0 2 +2H 2 0. 

Note .—Hypochlorites are strong oxidizing agents. See above reactions. 

In acid or alkaline solution hypochlorites act as free chlorine, a chloride 
iing formed and oxidation resulting of substances capable of being oxidized. 

Hypochlorites are distinguished from free chlorine by their 
saction with mercury, a reddish basic mercuric chloride, Hg 20 Cl 2 , 
sing found in place of white, HgCl. 

2. Heat a little KCIO in a small porcelain crucible. The salt 
‘maining is KC1, since oxygen gas has been liberated. 

3. (a) Add a little of the salt to a solution of indigo. Note 
lat the color is destroyed. 

( b ) Try the test with a weak solution of KMnC>4. Note 
lat the color remains. 

Note— Note distinction of chlorites from hypochlorites in the descriptive 
ction, pages 158, 159. 

NITRITE, N0 2 - 

1. Potassium Iodide Test with (a) Starch. —Acidify a solution 
[ KI and starch with dilute H2SO4 and add a few drops to a 
slution containing a nitrite. The reagent should be in sufficient 
mount to make the solution acid. A blue color results. (The 
xidizing nitrite liberates free iodine, which in turn forms a blue 
impound with starch.) 

(6) Carbon Disulphide— In place of the starch in the above 
-st use CS 2 and shake. CS 2 colored violet settles to the bottom 
f the solution. (CS2+I.) 


166 


QUALITATIVE ANALYSIS 


2. Decomposition with Acids.— (a) Dilute H 2 SO 4 decompose 
nitrites with liberation of nitric oxide. In presence of air N< 
oxidizes to brown NO 2 . Nitrates are not decomposed by dilut 
H 2 SO 4 . See test for nitrates in the Soluble Acid Group, page 201 

Reactions.—3NaN0 2 +3H 2 S04=HN0 3 +3NaHS04+ T 2NO+H 2 0, 
and NO+O = NOj brown gas. 

(b) Nitrites are decomposed by warming with acetic acic 
nitrates are not decomposed. 

3. Potassium Permanganate. —To an acid solution of KMnC 
add NaNC> 2 . The color is destroyed. Compare this test wit 
that of KCIO, Test 3 under Hypochlorite, on page 165. 

2KMn04+5NaN0 2 +3H 2 S04=K 2 S04+2MnS0 4 +5NaN0 3 +3H 2 0. 

4. Cobalt Salts. —Acetic acid solutions of cobalt salt produce 
a yellow precipitate, K3Co(N02)6. Make the test with a fairl 
strong solution of KNO 2 . 

Note. —See test for Cobalt under Ammonium Sulphide Group, pag< 
85, 103. 

5. Silver Nitrate precipitates white AgNC >2 from cold solution; 

KN0 2 +AgN0 3 = [ AgN0 2 +KN0 3 . 

6. Test in Water Analysis.—Acidify a dilute solution with 
drop or so of HC1, add 2 cc. of sulphanilic acid solution and 2 c< 
of naphthalamine hydrochloride. Nitrites cause a pink colors 
tion. This test is used in a quantitative determination in watt 
analysis. 

SILICATE, Si0 3 - 

1. Microcosmic Salt Test. —Fuse a little of the silicate sa 
with microcosmic salt in a platinum loop; the silica floats aroun 
in the bead, producing on cooling an opaque bead with weblik 
structure. 

2. Make a test with hydrofluouric acid according to directior 
given under detection of Silicon in the descriptive section, page 16! 






THE ACIDS 


167 


3. Insoluble Silicate.—Fuse with Na 2 C 03 -f K 2 CO 3 until effer- 
escence ceases. Add HC1 to acid reaction. Silicic acid is formed. 
Evaporate to dryness, add HC1, and dilute with water. The 
ases will dissolve, but silica is left as a gelatinous, insoluble 
ubstance. The precipitate Si0 2 warmed with CaF 2 and strong 
I2SO4 in a lead tube, liberates gaseous SiF 4 . If the gas is con- 
lucted into water gelatinous silicic acid is formed. 

3SiF 4 +3H 2 0 = 1 H 2 Si0 3 +2H 2 SiF 6 . 

SULPHIDE, S— 

1. Lead Acetate.—Add a few drops of dilute (1 :1) HC1 
,o the solid in a test tube and warm gently. Hold a filter paper 
noistened with Pb( 02 ^ 02)2 solution over the mouth of the tube. 
\ black discoloration is due to H 2 S. (PbS, black, formed.) 
Mote the characteristic odor of H 2 S. 

(a) FeS+2HCl = TH 2 S+FeCl 2 . 

(b) H 2 S+Pb(C 2 H 3 0 2 ) 2 = | PbS+2HC 2 H 3 0 2 . 

2. Oxidizing Agents.—Add concentrated nitric acid or HC1 
-fKC10 3 to a sulphide. Note liberation of sulphur. 

2HN0 3 +3H 2 S = | 3S+ t 2N0+4H 2 0. 

Further oxidation occurs on heating as follows: 

4S+8NH0 3 = 4H 2 S0 4 + T8N0. 

3. Silver Coin Tests for Insoluble Sulphide.—In case the 
above test is negative and a colored residue remains, wash and 
dry, fuse in a porcelain crucible with a piece of NaOH, dissolve the 
solid Na 2 S in a little water and place a drop on a silver com. A 
sulphide will leave a black stain (Ag 2 S). Write out reaction, 

4. Flame.—H 2 S burns with blue flame. 

2H 2 S+30 2 = T2S0 2 +2H 2 0. 


168 


QUALITATIVE ANALYSIS 


SULPHITE, S0 3 — 

1. Ferric Chloride Ferrocyanide Test.—Acidify the sulphite sal 
with dilute HC1 (using a test tube). Place a drop of a mixture 
of FeCl 3 and K 3 Fe(CN )6 in a loop tube and expose to the fume 
arising from the sulphite. The drop is colored blue [Fe 3 [Fe(CN)e ]2 
Turnbull's blue). Ferric chloride is reduced to ferrous state 
which reacts with K 3 Fe(CN) 6 . 

2. Sulphur Dioxide (a) Odor. —SO 2 is evolved when a sulphite 
is acidified. This can be recognized by its odor. 

Na 2 S0 3 +2HCl= T S0 2 +2NaCl4-H 2 0. 


(b) SO 2 is a strong reducing agent (see above). If passec 
into a solution of KMn(> 4 , it will decolorize the reagent. 

1 

2 KMn04-t-5S0 2 +2H 2 0=2MnS0 4 +K2S0 4 +2H 1 S04. 

(c) It is easily oxidized to the sulphate form by oxidizing agents 
such as bromine water or solution of iodine; the color is bleached. 


Br 2 +S0 2 +H 2 0 = H 2 S0 4 +2HBr. 

I 

(d) Sulphur dioxide conducted into an acid solution of K2Cr20? 
produces a green color due to reduction of chromic salt. (See 
chromium, page 94.) 

K 2 Cr 2 C> 7 +3SO 2 -j-H 2 SO 4 = Cr 2 (SO 4 ) 3 -}-K 2 SO 4 +H 2 0 . 

(See separation of sulphites and sulphates at the close of the tests 
of this group.) Thiosulphates liberate S as well as S0 2 ; sulphites 
liberate only SO 2 . 

THIOSULPHATE, S 2 0 3 — 

1. Acidify a little of the salt in a test tube with a few drops of 
HC1; S0 2 will be evolved (note the color) and free sulphur 
deposited. 

2Na 2 S 2 0 3 -f 4HC1 = | S0 2 + j S 2 +4NaCl+2H 2 0. 

Note .—With oxidizing agents present H 2 S also liberates free sulphur. 







THE ACIDS 


169 


Separation and Detection of Sulphate and Sulphite 


.cidify the cold solution and add BaCl 2 in excess. Filter. 


Precipitate.—BaS0 4 , white, 
roves presence of H 2 SO 4 . 

Filtrate contains the sulphite. Add Br 
water: a white ppt. of BaS0 4 proves the 
presence of a sulphite. (Sulphite oxidized to 
sulphate.) 

Analysis of Volatile Acid Group—Summary 

To a small amount of the solid unknown add dilute sulphuric acid. An 
:ffervescence will occur due to the liberation of gases. 

Reaction 


Inference 

)dor of rotten eggs, blackens lead acetate paper. 
Brown fumes, decolorizes KMn0 4 , iodine, etc. 
Liberates S0 2 and free sulphur. 

Liberates S0 2 , odor of the gas distinctive—burning S. 
Rapid effervescence, lime water made turbid. 

Chlorine evolved, noted by color and odor. 

Blight flocculent precipitate on adding water. 

HCN may be evolved—odor of bitter almonds (poison). 
Heating may cause acetic acid to evolve, also HCN, 
CO, 0, etc. 

H 2 S, sulphide. 

HN0 2 , nitrite. 

H 2 S 2 0 8 , thiosulphate. 
H 0 SO 3 , sulphite. 
H 2 C0 3 , carbonate. 
HC10, hypochlorite. 
H 2 Si0 3 , silicate. 


Exercises—The Volatile Acid Group 

1. If a sulphide and sulphite are both present in a sample, what product is 
formed when the material is acidified? 

2. How would you distinguish between a carbonate and a sulphite if 

both are present in solution? 

3. If a green color results when the gases evolved from an unknown, 
acidified with sulphuric acid, are passed into a solution of potassium dichro¬ 
mate, what gases are apt to be present? 

4. If, on testing for sulphides with lead acetate paper, a yellow color 

results, what is present in. the substance? 

5. How can you distinguish between a sulphite and sulphate? 

6. How can you distinguish between a nitrite and nitrate? 

7. How would you test for oxygen if a perchlorate were present in the 

substance being analyzed? 

8. State other methods for making confirmatory tests for H 2 b, »D 2 , <^ 2 , 
and CO 2 than the ones given under the exercises. Study Table of Reactions 

in Part V. 










SILVER NITRATE GROUP 

DESCRIPTIVE 


General Characteristics. 

Members of this group are precipitated by Silver Nitrate from 
solutions containing dilute nitric acid. These acids are not 
precipitated by Barium chloride. 

Individual Characteristics. 

CHLORINE AND ITS ACID COMBINATIONS 

Cl 2 , at.wt. 36.46; D. (air), 2.491; m.p. —101.6°; b.p. —33.6° C.; oxides, 

CI2O, CIO 2 , CI2O7. 

Hydrochloric Acid—HC1.—Mol. wt. 36.47; sp.gr. (air) 1.27; m.p. —112.5°; 
b.p. —83.1°. Solubility in 100 cc. H 2 0 at 10° is 82.5 g. Concentrated solu¬ 
tion of HC1 contains 40 per cent of the gas by weight (sp.gr. 1.20). At boiling 
point 20 per cent. 

Cl 2 “—At.wt. 35.46; sp.gr. (A) 2.49; m.p. -102°; b.p. 33.66°. Color, 
greenish yellow. Liberates Br and I from their salts. Causes starch iodide 
paper to turn blue, due to liberation of iodine. Decolorizes litmus. 

Chlorine occurs only in combination. It is found in all plants and animals; 
occurs in horn silver, AgCl; phosgenite, PbCl 2 ; in large quantities in carnel- 
lite, MgCl 2 +KCl+6H 2 0; sylvine, KC1; rock salt, NaCl; also combined 
with K, Na, Mg in sea water and salt springs. 

Salts.—Most chlorides are deliquescent except those of Ag, Hg, Pb, Cd, 
Co, Ba, Sr, K, Na, NH 4 . All soluble chlorides are readily transposed into 
carbonates by boiling with sodium carbonate, the insoluble salts by fusion 
with the dry Na 2 C0 3 . AgCl is not decomposed when heated to dull redness, 
but is decomposed by sulphuric acid and zinc, forming HC1, ZnS0 4 , and Ag. 

Although chlorides are nearly all soluble in water, silver chloride is practi¬ 
cally insoluble (100 cc. dissolves 0.000152 gram at 20° C.); mercurous chloride 
is nearly as insoluble as silver chloride (0.00031 gram); lead chloride requires 
heat to bring it into solution (in cold water only 0.673 gram soluble per 100 cc. 
of water). Chlorides of antimony, tin, and bismuth require free acid to keep 
them in solution. A large excess of HC1 increases the solubility of silver, mer- 

170 


THE ACIDS 


171 


ury, lead, antimony, bismuth, copper (Cu“), gold and platinum, but decreases 
he solubility of cadmium, copper (Cu - “),nickel, cobalt, manganese, barium, 
alcium, strontium, magnesium, thorium, sodium, potassium and ammonium 
hlorides. 

Chlorine gas is most readily dissolved in water at 10° C. (1 vol. H 2 O dis- 
olves 3.095 vols. Cl). Boiling completely removes chlorine from water. 

Hypochlorites, chlorites, chlorates, and perchlorates are soluble in water. 

The chlorine may be present either combined or free. In the combined 
;tate it may be present as free hydrochloric acid or as a water-soluble or insol- 
lble salt. 

DETECTION 


Free Chlorine.—The yellow gas is recognized by its characteristic odor, 
[t liberates iodine from iodides; it bleaches litmus, indigo, and many organic 
coloring substances. 

Chlorides. Silver Nitrate Test.—In absence of bromides and iodides, 
svhich also form insoluble silver salts, silver nitrate precipitates from solutions 
containing chlorides white, curdy, silver chloride, AgCl (opalescent with 
braces), soluble in NH 4 OH (AgBr slowly soluble, Agl difficultly soluble), also 
soluble in concentrated ammonium carbonate (AgBr is very slightly soluble; 
Agl is insoluble). Silver chloride turns dark upon exposure to light. 

Detection in Presence of Cyanate, Cyanide, Thiocyanate.—An excess of 
silver nitrate is added to the solution, the precipitate filtered Off and boiled 
with concentrated nitric acid to oxidize the cyanogen compounds and the 
white precipitate, silver chloride, subjected to the tests under chlorides to 
confirm the compound. 

Detection in Presence of Bromides and Iodides.—See Exercises, page 182. 
If Chlorates are Present.—The halogens are precipitated with silver 
nitrate, the precipitate dissolved with zinc and sulphuric acid and the solution 
treated as directed on page 182. 

Test for Hypochlorite.—Potassium hypochlorite, KCIO, shaken with mer- 
curv forms the yellowish-red compound Hg 2 OCl 2 , which does not form with 
the other potassium salts of chlorine, i.e., KC1, KC10 2 , KCIO?, KC10 4 . 

Hypochlorites decolorize indigo, but do not decolorize potassium perman¬ 
ganate solutions. If arsenous acid is present, indigo is not decolorized until 
all of the arsenous acid has been oxidized to the arsemc form. .... 
Tests for Chlorite.— Potassium permanganate solution is decolorized by 

chlorites. (The solution should be dilute.) 

A solution of indigo is decolorized, even in presence of arsemous acid 

(distinction from hypochlorites). ... , , , , ,• 

Detection of Chlorate— The dry salt heated with concentrated sulphuric 

acid detonates and evolves yellow fumes. 




172 


QUALITATIVE ANALYSIS 


Chlorates liberate chlorine from hydrochloric acid. 

Perchlorate. —The solution is boiled with hydrochloric acid to decompose 
hypochlorites, chlorites and chlorates. Chlorides are removed by precipi¬ 
tation with silver nitrate, the filtrate evaporated to dryness, the residue fusee 
with sodium carbonate to decompose the perchlorate to form the chloride, 
which may now be tested as usual. 


BROMINE 

Br, at.wt. 79.92; sp.gr. 3.1883°; m.p. -7.3°; b.p. 58.7° C.; acids, HBi 

HBrO, HBr0 3 . 

Hydrobromic Acid—HBr.— Mol.wt. 80.93; sp.gr. (air) 2.7+ , m.p. -86.13°, 
b.p.—68.7°. Solubility in 100 cc. H 2 0 at 0° is 221.2 g. Br 2 .—At.wt. 79.92, 
sp.gr. 3.188; m.p. —7.3°; b.p. 58.7°. 100 cc. of water at 0° dissolves 4.17 g. 

Hot water 3.5 gms. Soluble in CS 2 , ether, alkalies, alcohol, chloroform. 

The element is a dark, brownish-red, volatile liquid, giving off a dark 
reddish vapor with suffocating odor, irritating the mucous membrane (anti¬ 
dote dilute NH 4 OH, ether), very corrosive. Acts violently on hydrogen, 
sulphur, phosphorus, arsenic, antimony, tin, the heavy metals, and on potas¬ 
sium, but has no action on sodium, even at 200° C. Bleaches indigo, litmus, 
and most organic coloring matter. It is a strong oxidizing agent. Bromine 
displaces iodine from its salts, but is displaced by chlorine from its com¬ 
binations. 

Bromine never occurs free in nature. It is found chiefly combined with 
the alkalies and the alkaline earths, hence occurs in many saline springs and 
is a by-product of the salt industry. It is found in Silician zinc ores, Chili 
saltpeter, in sea water (probably as MgBr 2 ); in marine plants. Traces occur 
in coal, hence in gas liquors. 

The following facts regarding solubility should be remembered. The 
element bromine is very soluble in alcohol, ether, chloroform, carbon disulphide, 
carbon tetrachloride, concentrated hydrochloric acid and in potassium bromide 
solution. One hundred cc. of water at 0° C. is saturated with 4.17 grams of 
bromine, and at 50° C. with 3.49 grams. The presence of a number of salts 
increases its solubility in water, e.g., BaCl 2 , SrCl 2 , etc. 

Bromides are soluble in water, with the exception of silver, mercury, lead 
and cuprous bromides. 

Bromates are soluble in water with the exception of barium and silver 
bromates and some basic bromates. 

The soluble bromides are readily transposed by boding with Na 2 C0 3 ; 
the insoluble salts by fusion with dry Na 2 C0 3 . AgBr is not decomposed 









THE ACIDS 


173 


when heated to a dull redness, but when acted upon by Zn and H 2 S0 4 , forms 
HBr+ZnS0 4 +Ag. 

DETECTION 

Silver Nitrate solution precipitates silver bromide, AgBr, light yellow, 
from solutions containing the bromine anion. The precipitate is insoluble 
in dilute nitric acid, but dissolves with difficulty in ammonium hydroxide 
and is practically insoluble in ammonium carbonate solution (distinction from 
AgCl). 

Carbon Disulphide or Carbon Tetrachloride or Chloroform shaken with 
free bromine solution, or with a bromide to which a little chlorine water has 
been added (a large excess of chlorine must be avoided, as this forms BrCl 
compound), will absorb the bromine and become a reddish-yellow color, or 
if much bromine is present, a brown to brownish-black. In the latter case a 
smaller sample should be taken to distinguish it from iodine. 

Bromates are first reduced by a suitable reducing agent such as cold oxalic 
acid, sodium nitrite, hydrochloric acid, etc., and the liberated bromine tested 
as directed above. Silver nitrate added to bromates in solution precipitates 
AgBrOs, which is decomposed to bromine gas by hydrochloric acid. 

IODINE 

I, at.wt. 126.92; sp.gr. 4.948 17 °; m.p. 113.6°; b.p. 184.4° C.; acids, HI, 

HIO, HI0 3 , HI0 4 . 

The element is found free in some mineral waters; combined as iodides 
and iodates in sea water; in ashes of sea plants; small quantities in a number 
of minerals, especially in Chili saltpeter as sodium iodate, hence in the mother 
liquor from the Chilian niter works from which iodine is principally produced. 
Sea-weed ash (drift kelp, Laminaria digitata and L. stenophylla) is an impor¬ 
tant source of iodine. 

Hydriodic Acid—HI.—Mol.wt. 127.93; sp.gr. (air) 4.37; m.p.—51.3 ; 
b.p. —34.1°. Very soluble in water and in alcohol. 

1 2 .—At.wt. 126.92; sp.gr. 4.95; m.p. 114.2°; b.p. 184.35°. 

Very slightly soluble in water. Soluble in KI, CS 2 , alcohol, chloroform, 
ether. Gray black, rhombic solid. Occurs combined with K, Na, Ca, Mg, 
in certain salt springs and also in sea water. It is found in Chili saltpeter, 
in certain rock salts, in many plants, in muscle tissue, blood, milk, eggs, and 
in fresh water animals. It occurs rarely as Agl, Pbl in certain minerals. 

Iodides are easily soluble in water, with the exception of Agl, Hgl, Hgl 2 
and Pbl 2 . All soluble iodides are transposed by boiling with Na 2 C0 3 , the 




174 


QUALITATIVE ANALYSIS 


insoluble iodides by fusion with the dry carbonate. Agl is not decomposed 
when heated to dull redness. It is acted on by Zn and H 2 S0 4 , forming 
HI+ZnS0 4 +Ag, but the heat during a vigorous reaction will liberate free 
iodine. The element is liberated from its salts by Br and Cl; also by H 2 S0 4 , 
concentrated, and by certain oxidizing agents. 

DETECTION 

The element may be recognized by its physical properties. It is a grayish 
black, crystalline solid, with metallic lustre, brownish-red in thin layers. It 
vaporizes at ordinary temperatures with characteristic odor. Upon gently 
heating the element the vapor is evident, appearing a deep blue when unmixed 
with other gases, and violet when mixed with air. It colors the skin brown. 
Chemically it behaves very similarly to chlorine and bromine. 

Free iodine colors water yellow to black, carbon disulphide violet, ether 
or chloroform a reddish color, cold starch solution blue. 

Tannin interferes with the usual tests for iodine, unless ferric chloride is 
present. 

Iodide.—The dry powder, heated with concentrated sulphuric acid, evolves 
violet fumes of iodine. Iodine is liberated from iodides by solutions of As 5 , 
Sb 5 ,Bi 5 , Cu 2 , Fe 3 , Cr 6 , H 3 Fe(CN) 6 , HN0 2 , Cl, Br, H 2 0 2 , ozone. 

Insoluble iodides may be .transposed by treatment with H 2 S, the filtered 
solution being tested for the halogen. 

Iodate.—The acidulated solution is reduced by cold solution of S0 2 , or 
K 4 Fe(CN) 6 , (acidulated with dilute H 2 S0 4 ), or by Cu 2 Cl 2 , H 3 As0 3 , FeS0 4 , 
etc. An iodate in nitric acid may be detected by diluting the acid with water, 
adding starch solution, then hydrogen sulphide water, drop by drop, a blue 
zone forming in presence of the substance. 

HYDROCYANIC ACID, HCN 

Mol. wt. 27.02; sp.gr. 0.697; m.p.-15°; b.p. 26.1°. Very soluble in 
water, alcohol, ether, etc. 

C 2 N 2 .—Mol. wt. 52.02; sp.gr. 1.806 (A); m.p. —39°; b.p. —22°. 

Hydrocyanic acid exists in the seeds of certain plants. 

Commercial salts of cyanogen—KCN; K 4 Fe(CN) fl , yellow prussiate of 
potash; K 3 Fe(CN)e, red prussiate of potash. 

Prussic acid, HCN, and most cyanides are poisonous, and great care 
should be used in handling them. The cyanides of the alkaline earths and 
the alkalies and HgCN are soluble in water; most of the other cyanides are 
insoluble. All cyanides are transposed by boiling with Na 2 C0 3 . AgCN 
is insoluble in dilute HN0 3 , but soluble in KCN, NH 4 OH, or (NH 4 ) 2 C0 3 . 


THE ACIDS 


175 


It is decomposed when heated to dull redness, Ag 2 +C 2 N 2 being formed. 

' HCN is a weak acid and is liberated from its alkaline salts by organic acids. 

Detection.—See Laboratory Exercises, page 178. 

HYDROFERROCYANIC ACID, H 4 Fe+ + (CN)« 

A white crystalline powder soluble in water. Its principal salts, potassium 
ferrocyanide, ferriferrocyanide, Prussian blue, Fe 4 [Fe(CN)e] 3 . Ferrocyanides 
of alkalies and alkaline earths are soluble in water; most other ferrocyanides 
are insoluble in water and cold acids. They are transposed by boiling with 
Na 2 C0 3 or NaOH and are easily oxidized to ferricyanides by oxidizing agents. 
K 4 Fe(CN) 6 , boiled with concentrated H 2 S0 4 , is decomposed. HCN is 
liberated if the acid is dilute. Ag 4 Fe(CN) 6 , heated to dull red, is decom¬ 
posed, metallic silver being deposited. 

Detection. See Laboratory Exercises, page 179. 

HYDROFERRICYANIC ACID, H 3 Fe + + + (CN)« 

Brownish crystals. Its principal salts are potassium ferricyanide, and 
ferroferricyanide, Turnbull’s blue, Fe 3 [Fe(CN) 6 ] 2 . With exception of the 
alkalies and alkaline earths all ferricyanides are insoluble in water and in 
cold dilute acids. Dilute warm H 2 S0 4 causes a partical decomposition, 
HCN being liberated. Strong hot H 2 S0 4 liberates CO. Ferricyanides 
decompose, when highly heated, nitrogen and cyanogen gas being liberated 
and iron carbide and cyanide being formed. The ferricyanide may be reduced 
to the ferrocyanide. 

Detection. See tests under Laboratory Exercises, page 180. 

THIOCYANIC OR SULPHOCYANIC ACID, HCNS 

Mol. wt. 59.11; m.p. —12.5°. Very soluble in water. Colorless, irritating 
liquid. Colors ferric salts red, forming Fe(CNS) 3 . Other salts, KCNS, 
NaCNS, NH 4 CNS, Hg(CNS) 2 . The thiocyanates, with the exception of 
those of Ag, Hg, Pb, Cu, are soluble in water. AgCNS dissolves in an excess 
of NH 4 Oh! 

Detection tests given under Laboratory Exercises, page 180. 





176 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 

Use the potassium or sodium salts of the acids. 

CHLORIDE, Cl- 

1. (a) Silver Nitrate precipitates AgCl, white, curdy pre¬ 
cipitate from a solution containing a chloride. 

(b) AgCl dissolves in strong HC1. 

(c) The salt is insoluble in dilute HNO3. 

(d) The precipitate exposed to the light turns to a lavender 
and finally to a black color. 

(e) It is soluble in NH 4 OH, forming the readily ionized salt 
Ag(NH 3 ) 2 + Cl~. 

(/) It is reprecipitated upon acidifying the solution (e) with 
HN0 3 . 

( 1 g ) AgCl is soluble in (NH 4 ) 2 C 0 3 and KCN. 

Prove each of the statements by laboratory tests. Write out 
reactions. 

Note. —If chlorine is combined with silver decomposition may be accom¬ 
plished by adding metallic zinc and sulphuric acid and allowing the reaction 
to continue until the chloride is transposed. The solution is now filtered 
from metallic silver and may be tested for chloride. 

2 AgCl+Zn (+#H 2 SO 4 ) *= 1 2Ag+ZnCl 2 + (zH 2 SO 4 ) . 

2. Dichromate Test.—(a) Make a mixture of the dry chloride 
salt and K 2 Cr 2 07 , add concentrated H 2 S (>4 and heat. The red¬ 
dish brown gas is chromyl chloride. If the gas is now absorbed 
in NH 4 OH, ammonium chromate will form with its characteristic 
yellow color. Bromides and iodides do not interfere if present in 
moderate amount. 

Reactions— (a) 4NaCl+K 2 Cr 2 0 7 +6H 2 S0 4 = TCr0 2 Cl 2 +4NaHS0 4 
+2KHS0 4 +3H 2 0. 

(6) 4NH 4 0H+Cr0 2 Cl 2 = (NH 4 ) 2 Cr0 4 +2NH 4 Cl+2H 2 0. 


THE ACIDS 


177 


Note .—Bromine and iodine are liberated by the action of K 2 Cr 2 0 7 and • 
H 2 S0 4 . They combine with NH 4 OH, forming colorless ammonium salts. 

Study the section on detection of chlorine on page 171. 


BROMIDE, Br~ 


1. (a) Silver Nitrate precipitates AgBr from solutions con¬ 
taining the Br _ anion. 

( b ) AgBr is insoluble in dilute HNO 3 . 

(c) The light yellow precipitate darkens in the light. 

(d) It dissolves with difficulty in NH 4 OH and is insoluble in 
cold (NH 4 ) 2 CC> 3 . Prove statements by tests with a soluble base. 

2. Chlorine Test.—A water solution of the free halogen added 
drop by drop to a solution of a bromide salt liberates bromine. 
The free bromine may be recognized by adding carbon disulphide 
or chloroform and shaking the mixture, bromine colors the 
reagent yellow or reddish yellow. An excess of chlorine should be 
avoided, as the colorless BrCl would form. 

Reaction.—KBr+Cl = T Br+KCl. 

3. Potassium nitrate added to a bromide solution containing 
dilute H2SO4 does not liberate, bromine. Note distinction from 
iodide. 

IODIDE, I" 


1 ( a ) Silver Nitrate precipitates Agl from a solution of an 
iodide acidified with HN0 3 . 

(b) The yellow precipitate is insoluble in cold JNH 4 OII and 
in (NH 4 ) 2 C 0 3 . Make tests and write reaction. 

2. Chlorine Test. 1 — Carbon Disulphide, shaken with an iodine 
compound to which chlorine water has been added, is colored 
violet by the liberated iodine. CS 2 , being heavier than the solu- 


1 Iodine is also liberated from solutions of iodides by concentrated 
H2SO4, H 2 S0 4 +Mn0 2 , Na 3 AsO 3 +HNO 3 , ferric salts in a*dsolution, cupnc 
salts (2 CuS 0 4 +4KI = i 2CuI (yellowish brown) + I 2I+2K 2 bU4). 






178 


QUALITATIVE ANALYSIS 


tion, settles to the bottom of the containing vessel. As in case ol 
bromides an excess of chlorine should be avoided, since the colorless 
iodic acid would form. Prove this. 

Reactions.—KI+C1 = I-fKCl. 

1 2 +5C1 2 +6 H 2 0 = 2HIO 3 + 10HC1. 

3. Nitrite Test. —Potassium nitrite added to a solution of 
an iodide, acidified with H2SO4, liberates iodine. This may be 
recognized by the yellow color imparted to the solution or by 
absorbing in CS 2 , or CHCI 3 , a violet color becoming evident. 
The liberated iodine colors a dilute solution of starch blue. Note 
distinction from bromides. 

4. Potassium Dichromate sets iodine free from solutions of 
its salts containing a free acid. A few drops of dilute starch 
solution will cause a blue coloration due to the action of free iodine 
on starch. 

Reaction.— 6 KI-j-K 2 Cr 2 07 -l- 7 H 2 S 04 — 1 3 I 2 -{-Cr 2 (S 04 ) 3 -i' 4 K 2 S 04 -}- 7 H 20 . 

5. Mercuric Chloride Test. —HgCU precipitates scarlet Hgl 2 
from solutions of iodides. The compound is soluble in an excess 
of alkali iodide. 

(а) 2KI+HgCl 2 = 1 Hgl 2 (scarlet)+2KC1. 

(б) HgI 2 +2KI = K 2 HgI 4 . 


CYANIDE, CN- 

1. Silver Nitrate, added in excess to a cyanide, produces a 
white, flocculent precipitate, AgCN, soluble in KCN and in 
NH 4 OH, but is reprecipitated from these solutions by HNO 3 . 
Use a solution of KCN. 

Reactions.—(a) KCN+AgN0 3 = j AgCN+KN0 3 . 


(6) AgCN+KCN = KAg(CN) 2 . 


THE ACIDS 


179 


2. Ammonium Poly sulphide Test. Formation of Thiocyanate. 
—If few drops of (NH 4 ) 2 S X is added to a solution containing a 
cyanide, the mixture evaporated to dryness, then dissolved in 
HC1, and a few drops of FeCl 3 added, a red color, due to the 
formation of Fe(SCN) 3 , is obtained. The test may be carried 
out thus. Add to the cyanide a little dilute H2SO4 in a test tube, 
distill a few drops into a test tube containing about 1 cc. (NH 4 ) 2 S X . 
Evaporate to dryness in a small porcelain dish, cool, and add a 
drop of FeCl 3 . A red coloration will result due to ferric thio¬ 
cyanate formed. 

3. Formation of Prussian Blue— The alkali cyanide is made 
strongly alkaline with NaOH and a little FeS0 4 and FeCl 3 added, 
the mixture gently heated, then made acid with HC1 (Hood) 1 a 
precipitate of Prussian blue, Fe 4 (Fe(CN)e)3> is obtained. 

Reactions.—FeS 04 + 2 Na 0 H= J, Fe( 0 H) 2 +Na 2 S 04 . 

Fe(OH) 2 +6KCN= K 4 Fe(CN) 6 +2KOH. 

3K4Fe(CN)*+4FeCl 3 = Fe 4 [Fe(CN)6ls + 12KCl. 

FERROCYANIDE, (Fe + + (CN) 6 )-“ 

1. Silver Nitrate precipitates Ag 4 Fe(CN)6, white, insoluble 
in NH 4 OH. 

K 4 Fe(CN) 6 + 4AgN O 3 = | Ag 4 Fe(CN)6+4KN0 3 

2. Ferric Chloride, added to a solution of Fe(CN)a acidi¬ 
fied with HC1, produces a blue precipitate, Fe 4 [Fe(CN) fi ] 3 . decom¬ 
posed by NaOH, forming reddish brown Fe(OH) 3 . (FeS0 4 
produces a white precipitate easily oxidized to a light blue, due 
to the formation of a small amount of ferric salt.) 

3. Insoluble Ferrocyanide.—Solution is accomplished by boil- 

1 Should a cyanide be present HCN would be liberated. 





180 


QUALITATIVE ANALYSIS 


ing with sodium hydroxide. The hydroxide of the metal is pre¬ 
cipitated while sodium ferrocyanide will be in solution. Filter 
off the solution, acidify with HC1 and test for ferrocyanide by 
adding FeCl 3 as stated above. 

FERRICYANIDE, (Fe+ + + (CN)«)— 

Silver Nitrate precipitates reddish brown Ag 3 Fe(CN) 6 , soluble 
in NH 4 OH, and in KCN. 

Ferrous Sulphate, added to a solution of a ferricyanide acidified 
with HC1, forms a deep blue precipitate, Fe 3 (Fe(CN)e) 2 , Turn- 
bull’s blue. Ferric chloride gives a brown color with ferricyanides. 

Ferrous salts should be freshly prepared for the test by dis¬ 
solving pure iron in dilute H2SO4, with exclusion of air. See 
procedure under Iron in Part II, Metals, page 98. 

Note reducing agents, SO 2 , H 2 S, KI, etc., reduce ferricyanides 
to ferrocyanides. 

THIOCYANATE, CN“ 

Silver Nitrate precipitates white AgSCN, soluble in an excess 
of NH4OH. 

Ferric Chloride, added to a solution containing SCN acidified 
with HC1, produces a blood-red color due to the compound 
Fe(SCN)3. The color disappears upon the addition of HgCl 2 
solution, or Rochelle salts. 


THE ACIDS 


181 


I A systematic separation of the acids according to methods used in the 
lation of the metals has been found impracticable; the following methods of 
alysis of subgroups will be of value in distinguishing acids closely related. 

Analysis of the Silver Nitrate Group 

i Acidify the solution, prepared for acid analysis, with HN0 3 in excess, add 
;N0 3 . The precipitate that may form indicates the presence of any or all of 
e members of the group. Cl - , Br ,1 , CN , Fe(CN)e , Fe(CN)e 
the form of insoluble silver salts. 


Acidify a fresh portion of the solution with HC1 and add a few drops of 

3SO4. 

Blue precipitate forming immediately = Ferncyamde. Confirm. 

White precipitate turning blue =Fer rocyanide. Confirm. 

Test the original substance for HCN and KCNS. 


Detection of Ferro- and Ferricyanide and Thiocyanate in a Mixture.— 

cidify the solution with HC1, add FeCl 3 in excess, and filter. 

Precipitate.—Fe 4 [Fe(CN) 6 ] 3 , a Solution.-Red color is due to 

; 3 ep blue, Prussian blue. Fe(SCN) 3 . This color may be masked 

------— by the brown color produced by FeCl 3 

cting on Fe(CN) 6 . Extract the Fe(SCN) 3 by shaking with a little ether, 
'his will be colored red by the sulphocyanide. _ 

! To the solution add a few drops of SnCl 2 . The excess of the FeCl 3 is 
educed and reacts with the ferricyanide, forming the deep blue compound 
'e 3 [Fe(CN) 6 ] 2 , Tur nbull’s blue. _ ' _ 

! Xf CN - is present with the ferro and ferricyanides, add NaHCOs and 
istill. Test the distillate for CN according to one of the methods given. 
Caution .—HCN is extremely poisonous. Test in the hood. 

Insoluble double cyanides may be dissolved by boiling with NaOH. 


Detection of Chlorine, Bromine and Iodine 


If cyanogen compounds are present, they should be removed before testing 


or the halogens. 

Cyanides if present will give a white precipitate 
jrhese may be decomposed by boiling with HN0 3 . 


similar to that of chlorine. 






















182 


QUALITATIVE ANALYSIS 


Ferrocyanides and ferricyanides are removed by drying the precipitate ir 
porcelain crucible and heating to dull redness, cooling, and adding a piece 
zinc and a little H 2 S0 4 . Dilute and filter and add a few drops of HN0 3 a: 
AgN0 3 . The halogens will be precipitated free from the cyanides. 

Cyanides may also be removed by taking advantage of the insolubili 
of their nickel or cobalt salts, the halide salts being soluble. Add an excess 
nickel sulphate and filter. 

Precipitate.— Filtrate— Cl“, Br~, I“, S0 4 —, Ni + + . Add NaC 

Nickel cyanide. drop by drop as long as a precipitate takes place. Filter 


Precipitate.— Filtrate.—Cl“, Br~, I~, etc. Test the halides 1 

Ni(OH) 2 .—Reject, method of analysis given below. 


Methods for the Separation and Detection of the Halides 


A. Sulphate Method.—Acidify the filtrate, from which the cyanides ai 
nickel has been removed, by adding a few drops of H 2 S0 4 , and add ferric si 
phate (or ferric ammonium sulphate) and boil. 


Violet vapor of I 2 . 


When all of the iodine is expelled, add a crystal 
potassium permanganate and boil. 


Brown vapor of Br s 


When the bromine is completely expelled, filt 
and dilute the solution. Silver nitrate now added w 


precipitate white AgCl if chlorine is present. 


B. Persulphate Method.—Neutralize about 10 cc. of the solution wi 
acetic acid, adding 1-2 cc. in excess; dilute to six volumes and add abo 
half a gram of K 2 S 2 0 8 and heat. Test for free iodine by shaking with Ci 
(violet). If present, expel by boiling, adding more of the persulphate 
necessary. (Use casserole and boil 4-5 minutes.) When solution is colorles 
add more persulphate and boil again to be sure of the complete removal of 
Now liberate bromine by adding 2-3 cc. H 2 S0 4 (dilute), and a little mo 
K 2 S 2 0 8 , and heat almost to boiling. If the solution is colored yellowish re> 
bromine is indicated. Confirm by testing a few cc. in a test tube with C» : 
(colored yellow or red). If Br is present, add 0.5 g. more of the persulpha 
to the main solution and expel Br by boiling. The volume of the solutic 
should be kept about 60 cc., so that distilled water should be added to repla< 
that lost by evaporation. When Br has been expelled, cool and add a fe 
drops of AgN0 3 . A white precipitate indicates chlorine. 


















THE ACIDS 


183 


In the presence of chlorates, the halogens should be removed by precipi- 
ing with AgN0 3 , filtering, and dissolving the precipitate by means of Zn 
d H 2 SO 4 . This solution may be now tested by the perchlorate method. 
Magenta Test.—The test reagent is made by adding 10 cc. of 0.1 per cent 
lution of magenta to 100 cc. of 5 per cent solution of sulphurous acid and 
owing to stand until colorless. This is the stock solution. Twenty-five cc. 
this reagent is mixed with 25 cc. of glacial acetic acid and 1 cc. of sulphuric 
id. Five cc. of this is used in the test. 

Test.—Five cc. of the magenta reagent is mixed with 1 cc. of the solution 
sted. Chlorine produces a yellow color. Bromine gives a reddish-violet 
tloration. The colored compound in each case may be taken up with chloro- 
rm or carbon tetrachloride and a colorimetric comparison made with a 
andard. 

In halogen mixes, iodine is first eliminated by heating with an iron per 
ilt. Bromine is now liberated by adding sulphuric acid and potassium 
iromate. A glass rod with a pendant drop of sodium hydroxide is held 
l the vapor to absorb bromine, and the drop then tested with the magenta 
iagent. After iodine and bromine are eliminated, chlorine may be tested 
y heating the substance with potassium permanganate, which liberates this 
alogen. 


LABORATORY REVIEW 


1 . CIO 3 is removed from a solution of halides on account of its action on 

ree iodine. What is this action? ... 

2. Explain why the difficultly soluble silver halides dissolve in dilute 

ulphuric acid when zinc is added. 

3. From the solubility table devise a method of separating chlorine from a 


errocyanide. 

4. How can free chlorine in 
ihlorine? 

5 . How would you distinguish 


solution be distinguished from combined 
between a chloride, a bromide and an 


d 6 . e? Give a procedure for detecting the halides in a mixture containing 
llorine, bromine and iodine combined as salts. . 

7. Give a procedure for detecting H 2 S in an insoluble sulphi e. 

8 . How can you distinguish (a) A ferrocyanide from a ferricyamde. (*) 
cyanide from a carbonate? 

9 Give a procedure for testing a thiocyanate. Q .» 

10. Study the Table of Reactions—Inorganic Acids—under the Silver 

itrate Group, Part V. 



BARIUM CHLORIDE GROUP 


DESCRIPTIVE 


General Characteristics. 


Members of this group are precipitated by BaCl2 from neutn 
solutions. The Sulphate and the Fluoride of Barium are insolub 
in dilute nitric acid, and in dilute hydrochloric acid. 


Individual Characteristics. 


Arsenous Acid and Arsenic have already been taken up in connnectic 
with arsenic in the Soluble H 2 S Subgroup. If arsenic has been found, thes 
acids are likely to be present. 

Arsenic Acid.—H 3 As0 4 .—Mol.wt. 151.03; sp.gr. 2.5; m.p. 35.5°; b. 
H 3 As0 4 H 2 0, 160°. The acid dissolves readily in water and alkalies. 


BORON 


B, at.wt. 11.0 


amorp. sp.gr. 2.45 ; m.p. 2200°; b.p. sublimes, 
cryst. sp.gr. 2.55; m.p. 2500°; b.p. 3500° C.; oxide, B 2 0 


Crystalline boron is scarcely attacked by acids or alkaline solutions; tl 
amorphous form, however, is soluble in concentrated nitric and sulphur 
acids. Both forms fused with potassium hydroxide are converted to pota 
sium metaborate. 

Boric Acid—H ;i B0 3 .— Mol. wt. 62.02; sp.gr. 1.435; m.p. 184°-186°. 

Boracic acid occurs free in the mineral sassolite, and to some extent i 
mineral waters (Tuscany springs). The borates are derived from tetrabor 
acid. Ordinary borax, Na 2 B 4 0 7 • 10H 2 O, is one of its familiar compound 
The ortho, H 3 B0 3 , meta, HB0 2 , and tetra or pyro, H 2 B 4 0 7 , respond to tl 
same tests. 

Boric acid is more readily soluble in pure water than in hydrochlori 
nitric, sulphuric, or acetic acids, but more soluble in tartaric acid. It 
soluble in alcohol and volatile oils. Borax is insoluble in alcohol. Wit 
acids it becomes transposed to boric acid and the sodium salt of the acid. 

Most borates of the alkalies are soluble in water, and have an alkalin 
reaction due to the slight dissociation of boracic acid. Other borates are nc 

184 





THE ACIDS 


185 


I ldily soluble in water, but dissolve in inorganic acids. Most borates, 
>on heating, expand, then fuse into a transparent form. Only one of the 
drogen atoms is replaceable by metals. Most of the boron compounds 
ow a great similarity to the corresponding silicon compounds. 


DETECTION 


Flame Test—Boric acid is displaced from its salts by nearly all acids, 
eluding even carbonic acid. Upon ignition, however, it in turn drives out 
her acids which are volatile at lower temperatures. A powdered borate, 
•eviously calcined, is moistened with sulphuric acid and a portion placed on 
te loop of a platinum wire is heated to expel the sulphuric acid, then moistened 
ith glycerine and placed in the colorless flame; a green color will be imparted 
, the flame. Copper salts should be removed with H 2 S and barium as BaS0 4 
present, as these also color the flame green. 

The flame test may be conveniently made by treating the powdered sample 
L a test tube with sulphuric acid and alcohol (preferably methyl alcohol). A 
Lrk carrying a glass tube is inserted and the test tube gently warmed. The 
scaping gas will burn with a green flame. 

The test may be made by igniting the mixture of powder, alcohol, and sul- 
huric acid in an open porcelain dish. The green color will be seen in presence 
f a borate. The test is not as delicate as the one with the test tube. 

Borax Bead.— Na 2 B 4 O 7 -10H 2 O fused in a platinum loop, swells to several 
imes its original volume as the water of crystallization is being driven out, 
hen contracts to a clear molten bead. If the bead is dipped mto a weak 
olution of cobalt and plunged into the flame, until it again becomes molten, 


le bead upon cooling will be colored blue. ... 0 

Turmeric Test—A few drops of acetic acid are added together with 2 
r 3 drops of an alcoholic turmeric solution to an alcoholic extract of the 
imple, placed in a porcelain dish. The solution is diluted with water and 
hen* evaporated to dryness on the water bath. 1/1000 milligram of bone 
cid will produce a distinct color, 2/100 milligram wdl give a strong reddish- 
rown colored residue, which becomes bluish-black when treated with a drop 
f sodium hydroxide solution. 


CHROMIC ACID AND CHROMATES 

The student is referred to the section on Chromium, under the Ammonium 
ulphide Group, Part II, The Metals, for the review of this element and its 

3 id combinations, pages 83, 94. , , , Chromic 

Chromic Hydroxide, Cr(OH) 3 , is an amphoteric electrolyte. Chromic 

a °form violet crystals, producing a violet solution which becomes green 
hen boiled. 





186 


QUALITATIVE ANALYSIS 


Chromic acid forms red needles which decompose in a warm solutio 
Cr0 3 +H 2 0 resulting. 

Chromates form yellow crystals and color a solution yellow. The chr 
mates of the heavy metals and of Ba are insoluble in water. The alb 
chromates and the chromates of Mg and Ca are soluble. All chromat 
are transposed by boiling with Na 2 C0 3 . 

Insoluble Chromium Compounds.—These are brought into solution 1 
fusing the solid with Na 2 C0 3 and a little KC10 3 . The mass extracted wi 
water will give a solution of a chromate and a residue of the metals. 

DETECTION 

All solutions containing chromates are orange or yellow colored. A redu 
ing agent such as H 2 S, S0 2 , alcohol in presence of an acid produces a gre< 
color. Warming may be necessary to hasten the reaction. See laboratoi 
exercises for tests and reactions, page 194. 

FLUORINE 

F“, at.wt. 19; D (air) 1.31 15 °, sp.gr. (-187°) 1.14; m.p. -223; b.p. -187°C 

acids, HF, H 2 SiF 6 . 

Fluorine, F. The univalent element is a greenish yellow poisonous ga 
It decomposes cold and hot water. It occurs in the minerals fluor spa 
CaF 2 ; cryolite, 3NaF+AlF 3 and to a slight extent in mineral spring 
ashes of plants, in bones and teeth as CaF 2 . 

The determination of fluorine in the evaluation of minerals used for tl 
production of hydrofluoric acid is of technical importance. The demand f( 
elimination of the use of fluorides for preservatives of food makes its detectic 
important. 

Fluorides of the alkalies except lithium and of Ag, Al, Hg, Co, Ni, SI 
Sn (ous) are readily soluble; copper, lead, zinc, and iron fluorides are sparing] 
soluble; the alkaline earth fluorides dissolve in 100 cc. H 2 0 as follow 
BaF 2 = 0.163 gram, SrF 2 = 0.012 gram, CaF 2 = 0.0016 gram. 

Fluosilicates of potassium, sodium, and barium are slightly soluble i 
water and practically insoluble if sufficient alcohol is added. 

Fusion of the calcium salt CaF 2 only partially transposes the compoun< 
In presence of silica the action may go to completion. 

Hydrofluoric Acid, HF.—Mol. wt. 20.01; sp.gr. 0.71260°; m.p. —92.3 
b.p. 19.44°. Hydrofluoric acid is a colorless, mobile liquid which fumes i 
the air. It readily attacks glass, hence must be kept in vulcanite, paraffin 
or platinum vessels. 


THE ACIDS 


187 


DETECTION OF FLUORIDE 

Fluorine is the most active element known, and is by far the most active 
the halogens, displacing chlorine, bromine, and iodine from their combina- 

>ns. . 

Etching Test.—The procedure depends upon the corrosive action of hydro- 
oric acid on glass, the acid being liberated from fluorides by means of hot 
ncentrated sulphuric acid. This test is applicable to fluorides that are 
composed by sulphuric acid. The reactions taking place may be repre- 
nted as follows: 

I. CaF 2 +H 2 S0 4 = CaS0 4 +2HF. 

II. Si0 2 +4HF = 2H 2 0+SiF 4 . 


I The test may be carried out in the apparatus shown in the illustration 
i this page. A clear, polished glass plate 2 ins. square, free from scratches, 
warmed and molten wax allowed to 


jw over one side of the plate, the ex- 
iss of wax being drained off. A small 
,ark is made through the wax, expos- 
tg the surface of the plate, care being 
iercised not to scratch the glass. If 
■ie test is to be quantitative, the marks 
should be of uniform length and width. 

5 he powdered material is placed in a 
j^rge platinum crucible B (a lead cruci- 
le will do); sufficient concentrated sul- 
, huric acid is added to cover the sample. 

5 'he plate (D) with the wax side down 
jj placed over the crucible and pressed 
irmly down. To prevent the wax 
com melting, a condenser with flowing 
Vater, cools the plate. An Erlenmeyer 
ksk \C) is an effective and simple form 
' if condenser, though a metallic cylinder 
3 a better conductor of heat. A little 
Tvater placed on the plate makes better 
, ;ontact with the condenser. As a further 
protection a wide collar of asbestos 
poard (E) may be placed as shown in 
-he figure. In quantitative work, where i 
sary, the crucible is placed in a casserole 



Fig. 15.-Etching Test for Fluorine. 


l careful regulation of heat is neces- 
with concentrated sulphuric acid or 

















188 


QUALITATIVE ANALYSIS 


It 

1 1 


in a sand bath, containing a thermometer to register the temperature. Th 
run is best conducted at a temperature of 200° C. (not over 210°—H 2 SO 
fumes). After an hour the wax is removed with hot water and the plat 
wiped clean, and examined by reflected light for etching. A test is positiv 
when the mark can be seen from both sides of the glass. Breathing over th 
etched surface intensifies the mark. 

Treatment of Fluo-Silicates not Attacked by Sulphuric Acid.—The pov 
dered material is mixed with about eight times its weight of sodium cai 
bonate and fused in a platinum crucible. The cooled melt is extracted wit 
water. Calcium fluoride is thrown out from the filtrate. The fluoride may no> 
be tested as directed in the etching test or as follows by the hanging dro 
test. 

The Hanging Drop Test.—The test depends upon the reaction 3SiF 4 +3H 2 ( 
= 2H 2 SiF 6 +H 2 Si0 3 . 

If the material contains carbonates, it is calcined to expel carbon dioxide 
Half a gram of the powdered dry material is mixed wit 
0.1 gram dried precipitated silica and placed in a tes 
tube, Fig. 16, about 5 cm. long by 1 cm. in diameter, i 
one-hole rubber stooper fits in the tube. A short glas 
tube, closed at the upper end, passes through the stoppe 
extending about 3 mm. below. Two or three drops o 
water are placed in this small tube by means of a pipette 
nearly filling it. Two cc. of concentrated sulphuric aci< 
are added to the sample in the test tube and this im 
mediately closed by inserting the stopper carrying th 
hanging drop tube, exercising care to avoid dislodginj 
the drop of water. The test tube is placed in a beake 
of boiling water and kept there for thirty minutes. I 
an appreciable quantity of fluorine is present a heaw 
gelatinous ring of silicic acid will be found at the end o 
the hanging drop tube in the stopper. 

It is important to have material, test tube, and rubbe 
stopper dry, so that the deposition may occur as stated. 

Note. —Dr. Olsen makes the test by heating the sampl 
in a small Erlenmeyer flask, with concentrated sulphur! 
acid. A watch-crystal with a drop of water suspended on its curved surfac 
is placed over the mouth of the flask. A spot etch is obtained in presence o 
fluorine. 

Black Filter Paper Test.—According to Browning, small amounts o 
fluorine may be detected by the converse method for detection of silicate 
and fluosilicates (see Silicon). The fluoride is placed with a suitable amoun 


» 


Fig. 16.—Hanging 
Drop Test for 
Fluorine. 













THE ACIDS 


189 


of silica, in a small lead cup, 1 cm. in diameter and depth (Fig. 14, page 
161); a few drops of concentrated sulphuric are added; the cup is covered 
by a flat piece of lead with a small hole in the center; upon the cover is 
placed a piece of moistened black filter paper and upon this a small pad of 
moistened filter paper. The cup is heated on the steam bath for ten 
or fifteen minutes. A white deposit will be found on the under side of 
the black filter paper, over the opening in the cover, if fluorine is present 
in an appreciable amount. (0.001 gram CaF 2 and 0.005 gram Na 3 AlF 8 
will give test.) 


PHOSPHORUS AND ITS ACID COMBINATIONS 


yellow 1.831 # 


P 4 , at.wt. 31.04; sp.gr. red 2 296 ; m -P- 725 


44 c 


; t>-p- 


230°C. 


; oxides, 


P 2 0 3 , P0 2 , P2O5; acids, H3PO2, H3PO3, II3PO4, HPOs, H4P2O7. 


Phosphoric Acid, H 3 PO 4 .—Phosphorus forms a number of acids—hypo, 
meta, ortho, and pyrophosphoric and hypo, meta, and pyrophosphorous acids. 
Orthophosphoric acid, H 3 P0 4 , is the most stable in solution. The other 
phosphoric acids are converted into the ortho form by boiling with water, 
i Mol.wt. 98.02; sp.gr. 1.88; m.p. 38.6°. Orthophosphoric acid is very soluble 
I in water. It is a tribasic acid, and has consequently three series of salts. 
I The phosphates occur principally as calcium phosphate, Ca 3 (P0 4 ) 2 , in minerals 
1 and in bones; in iron they occur as Fe 3 (PO 4 ) 2 - Phosphates are found in both 
|j plants and animals. The phosphates of the alkalies are soluble in water, 
:! whereas the normal phosphates of the metals are insoluble but are readily 
ij soluble in mineral acids. 


DETECTION 

Element.—Phosphorus is recognized by its glowing (phosphorescence) in 
the air. The element is quickly oxidized to P 2 G 6 ; if the yellow modification 
is slightly warm (34° C.) the oxidation takes place with such energy that the 
substance bursts into flame. The red form is more stable. It ignites at 

260° C. , . , . , 

Boiled with KOH or NaOH it forms phosphine, PH.;, which in presence of 

accompanying impurities is inflammable in the air. 

Phosphorus oxidized to P 2 0 6 may be detected with ammonium molybdate, 
a yellow compound, (NH 4 ) 3 P0 4 - 12Mo0 3 -3H 2 0, being formed. 

Acids. Hypophosphorous Acid, H 3 P0 2 , heated with copper sulphate^ to 
55° C. gives a reddish-black compound, Cu 2 H 2 , which breaks down at 100° to 
H and Cu. Permanganates are reduced immediately by hypophosphorous 






190 


QUALITATIVE ANALYSIS 


acid. No precipitates are formed with barium, strontium or calcium solutions. 
Zinc in presence of sulphuric acid reduces hypophosphorous acid to phosphine, 
PH 3 . 

Phosphorous Acid, H 3 P0 3 .—Copper sulphate is reduced to metallic copper 
and hydrogen is evolved, no Cu 2 H 2 being formed as in case of hypophosphorous 
acid. Permanganates are reduced slowly. Added to solutions of barium, 
strontium or calcium white phosphites of these elements are precipitated. 
Alkali phosphites are soluble in water, while hypophosphites are not readily 
soluble. 

Orthophosphoric Acid, H 3 P0 4 .—Ammonium phosphomolybdate precipi¬ 
tates yellow ammonium phosphomolybdate from slightly nitric acid solutions. 
The precipitate is soluble in ammonium hydroxide. 

Metaphosphoric Acid, HP0 3 .—Converted by nitric acid in hot solutions 
to the ortho form. Metaphosphoric acid is not precipitated by ammonium 
molybdate. 

Pyrophosphoric Acid, H 4 P 2 0 7 .—Converted to orthophosphoric acid in hot 
solutions by nitric acid. No precipitate is formed with ammonium molybdate. 


Comparison of Ortho, Meta and Pyrophosphoric Acids 


Reagen t 

Orthophosphoric 

acid 

Metaphosphoric 

acid 

Pyrophosphoric 

acid 

Ammonium molybdate. 

Albumin. 

Yellow ppt. 

No ppt. 
Coagulated 

No ppt. 

Not coagulated 

Zinc sulphate, cold, in excess . . . 


No ppt. 

White ppt. 

Silver nitrate in neutral solution. 

Yellow ppt., 

White ppt., 

White ppt., 


Ag s P0 4 

AgPO. 

Ag 4 P 2 0 7 

Magnesium salts. 

White ppt. 

No ppt. 

No ppt. 


Phosphorous acids are distinguished from phosphoric acids by the phos¬ 
phine formed with the former when acted upon with zinc. 

Acid phosphates are distinguished from normal phosphates as follows: 
Neutral silver nitrate added to an acid phosphate liberates free nitric acid 
(litmus test), the following reactions taking place: 

3AgN0 3 +Na 2 HP0 4 = Ag 3 P 0 4 + 2 NaN 03 +HN 0 3 . 

The solution resulting when silver nitrate is added to normal phosphate 
solution is neutral. 

3 AgN 03 +Na 3 P 04 = Ag3P0 4 +3NaN0 3 . 















THE ACIDS 


191 


SULPHURIC ACID, H 2 S0 4 

Mol.wt. 98.09; sp.gr. 1.834; m.p. 10.5°. The acid in its anhydrous solid 
state forms prismatic crystals. It dissolves in water in all proportions. 

H 2 S0 4 -II 2 0 (cone, acid).—Sp.gr. 1.788; m.p. 8.53°; b.p. 210°-338°. 

H 2 S0 4 *2H 2 0—Sp.gr. 1.655; m.p. —38.9°; b.p. 170°-190°. 

Sulphuric acid occurs in the free state to a trivial extent in certain volcanic 
springs. It occurs very abundantly combined as sulphates, gypsum, 
CaS0 4 -2H 2 0; barytes, BaS0 4 ; celesite, SrS0 4 , sulphates of the alkalies 
in animal and plant fluids. The acid in pure form is a thick, colorless fluid 
having a great affinity for water. As it is a dibasic acid, it has two series of 
salts. Most of the metals except Pb, Pt, Au, and certain of the rare metals 
| are dissolved by dilute sulphuric acid. Most sulphates are soluble in water; 

those of Ag, Ca, Sr, Pb, and Ba are but slightly soluble in water, the solubility 
i decreasing in the order given. Most basic sulphates are insoluble. Na 2 C0 3 , 

‘ fused with a sulphate, transposes it into the soluble sodium salt. Ordinary 
boiling with an alkaline carbonate will accomplish this change, but in case of 
i BaS0 4 the carbonate is best formed by fusion. Sulphates may be reduced by 
: charcoal and fusion mixture to sulphides of the alkalies with exception of the 
alkali and alkaline earth sulphates, most sulphates are decomposed by heat, 
SO 3 or S0 2 or both being evolved while the oxide of the metal remains. 


detection 

Sulphate.—A white compound, BaS0 4 , is precipitated in presence of free 
hydrochloric acid when a solution of barium chloride is added to a solution of 

Insoluble sulphates are decomposed by boiling or fusion with alkali car¬ 
bonates, forming water-soluble alkali sulphates. 

Free sulphuric acid may be detected by evaporating the solution, alter 
addition of a few grains of sugar, to near dryness. The mixture turns^dar 
as the concentrated acid, when in contact with organic matter, extracts the 
elements of water and leaves carbon. 

Note —For other compounds of sulphur, see pages 162, 168. 


192 


QUALITATIVE ANALYSIS 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 

ARSENITE, As 0 3 , AND ARSENATE, As0 4 

Test. —Acidify and pass in H 2 S. A slight yellow precipitate 
forming slowly indicates an arsenate, AS 2 S 5 . A copious yellow pre¬ 
cipitate indicates AS 2 S 3 , arsenite. 

The student is referred to the section on Arsenic under Metals 
in Part II for tests and reactions. 

Distinction between Arsenite and Arsenate 

(a) Arsenite. —No precipitate is obtained with either ammo¬ 
nium molybdate or with magnesia mixture. Note reaction with j 
arsenates. Silver nitrate precipitates yellow silver arsenite, 
Ag 3 As0 3 . (Distinction from arsenate, Ag 3 AsC> 4 , chocolate brown.) 
Phosphate of silver is also yellow. 

Reaction.—Na 3 As0 3 +3AgN0 3 = | Ag 3 As0 3 +3NaN0 3 . 

(b) Arsenate. —Precipitates are obtained with ammonium 
molybdate and with magnesia mixture (distinction from arsenites). 
Similar precipitates are obtained with phosphates. The pre¬ 
cipitate with magnesia mixture, white crystalline NH 4 MgAs0 4 
may be distinguished from NH 4 MgP0 4 by the fact it is 
rendered reddish brown by treatment with AgN0 3 reagent 
(Ag 3 As0 4 formed). The precipitate with ammonium molybdate 
(NH 4 ) 3 As0 4 - 12 Mo 0 3 ) forms more slowly and requires warming 
to a higher temperature for complete precipitation than does 
the phosphate compound. 

Reactions: (a) H 3 As0 4 +12(NH 4 ) 2 Mo0 4 +21HN0 3 = 

1 (NH 4 ) 3 As0 4 12Mo0 3 +21NH 4 N0 3 + 12H 2 0. 

(b) Na 3 As0 4 +MgCl 2 +NH 4 Cl = j NH 4 MgAs0 4 +3NaCl. 



THE ACIDS 


193 


Silver Nitrate precipitates chocolate-colored Ag3As0 4 when 
added to neutral solutions of arsenates. (Arsenites and phos¬ 
phates of silver are yellow.) 


BORATE, BO 3 

1. Precipitation Test with Barium Chloride. —Add the reagent 
to a borate solution. The white precipitate is barium metaborate, 
Ba(B 02 ) 2 , soluble in excess of the reagent, in acids, and in ammo¬ 
nium chloride. The solution of the borate should be concentrated. 

Reaction.—NaaB^r+BaCh-bSHoO = 1 Ba(B 02 ) 2 + 2 H 3 B 03 + 2 NaCl. 

| Note .—AgNOs added to a concentrated cold solution also gives a white 

precipitate of AgB 02 soluble in NH 4 OH and in HNO 3 . 

2. Alcohol Flame Test. —Mix a borate in a thin paste witii 
concentrated H 2 S0 4 and a little alcohol; on being ignited the 
alcohol is tinged with a green color, due to the volatile compound, 
(C 2 H 5 ) 3 B 03 , being formed. The experiment may be performed 
in a test tube; the solid added and made into a paste with H 2 S0 4 . 
A one-hole stopper, with a glass tube drawn out to capillarity 
at the free end is placed in the test tube upon the addition of a 
little alcohol. When the solution is warmed and the issuing gas 
rejected into the opening at the base of a Bunsen burner, a green 
flame will be produced if a borate is present. 

Reaction.—H 3 BO 3 -I- 3 C 2 H 5 OH | (C 2 H&) 3 B 03 -t- 3 H 20 . 

N 0 t e .—Silicates containing boron are decomposed by adding a little 
calcium fluoride and sulphuric acid, BF 3 is volatilized on heating and colors 
the Bunsen flame green. 

3 Turmeric Test. —Moisten a portion of a piece of turmeric 
paper with an acidified (HC1) solution of a borate, and dry on a 
watch glass. The portion moistened is colored brownish red or 
pink. A drop of NaOH causes this to change to a greenish brown 
or black. The unmoistened portion serves as a control. 




194 


QUALITATIVE ANALYSIS 


Notes .—Oxidizing agents such as chlorates, iodides, chromates, destroy 
the turmeric, hence should not be present. HN0 3 does no harm. HC10 3 
and H 2 Cr 04 may be reduced in dilute HC1 solution with Na 2 S0 3 . 

FeCl 3 colors the turmeric paper brown. 

4. Borate Ignited.—Dip a platinum wire with loop into water 
and then into powdered borax. Place in a flame and note that 
the salt swells (escape of water) and then fuses in a clear bead. 
If the bead is moistened with a solution of cobalt salt and again 
heated a blue-colored bead is obtained. 

Na 2 B 4 O 7 -f CoO = Co(B0 2 ) 2 (blue) +2NaB0 2 . 

CHROMATE, 1 Cr0 4 — 

1. Chromate and chromic acid have been mentioned under 
chromium. (See Ammonium sulphide group, page 83, 94.) 
Chromates are all red or yellow. The acid solutions are red 
(dichromate) and the alkaline solutions yellow (chromate). The 
color is evident in very dilute solutions and is characteristic; a 
colorless solution, therefore, does not contain a chromate. 

Determine the sensitiveness of the color test for a chromate, 
using K 2 CrC> 4 . See page 210—Reaction Limits. 

2. Reducing Agents change yellow chromates into green chro¬ 
mium salts, e.g., from acidic to basic chromium. To an acid 
solution of a chromate add a little alcohol and boil. Note the 
change of yellow to green. 

Reaction.—K 2 Cr 2 0 7 (orange) +3C 2 H a OH-|-8HCl = 2CrCl 3 (green) 

+ T 3H 3 CHO+2KC1+7H 2 0. 

3. Hydrogen Peroxide.—Acidify a very dilute solution of H2O2 
with dilute H2SO4. Add about 4 cc. of ether and then a few drops 
of a dilute chromate solution. A blue coloration is produced by 
chromate or dichromate. On shaking, the ether takes up the 
blue compound (HCr 04 ), forming a brilliant blue layer. 


1 See Descriptive Section for Insoluble Chromium Compounds. 



THE ACIDS 


195 


4. Barium Chloride Test.— Add the reagent to an acidified 
(HNO3) solution of a chromate together with 4-5 cc. of NaC2Hs02 
solution; the yellow precipitate is BaCrC> 4 . Write out reaction. 

Note .—If SO4 , P0 4 , CrC >4 , or C 4 H 4 O 6 are present, make 

alkaline with NH 4 OH and add 1-2 cc. of CaCh and shake. Filter after 
10-15 minutes. Acidify filtrate with HN0 3 and test for chromate. 

5. Lead Acetate Test. —Add the reagent to a solution of 
K 2 Cr 04 . The yellow precipitate is PbCrC> 4 . Write the reaction. 

6 . Silver Nitrate Test. —The reagent added to a neutral solu¬ 
tion gives the purplish-red silver chromate, soluble in HNO3 and 
j in NH4OH. The reddish-brown dichromate is precipitated from 

concentrated solutions, faintly acid. Write out reactions with 
K 2 Cr 04 and K 2 Cr 207 . 

FLUORIDE, F 

Use an alkali fluoride for the tests. 

1. Precipitation Tests, (a) Barium Chloride .— Add the reagent 
to the solution of a fluoride. The white precipitate is BaF 2 . Test 
solubility in HC 1 or HNO3. Does the precipitate dissolve in a 
solution of NH4CI? 

(b) Calcium Chloride. —To an aqueous solution of a fluoride 
add CaCl 2 solution. The white precipitate is CaF 2 . The com¬ 
pound is difficultly soluble in HNO 3 and in HC1. It is practically 
insoluble in acetic acid. 

Reaction.—2 KF+CaCl 2 = i CaF 2 (white) +2KC1. 

2. Etching Tests.— Consult “ Detection ” of Fluorides under 
the descriptive section for Fluorine, page 187. 

(a) Action of H2SO4 on a fluoride. 

CaF 2 +H 2 S0 4 = i CaS0 4 + T 2HF. 

Silica in glass is acted on as follows: 

Si0 2 +4HF = T SiF 4 +2H 2 0. 

( b ) Action of H 2 O on SiF 4 : 

3SiF 4 +4H 2 0 = | H 4 Si04+2H 2 SiF«. 




196 


QUALITATIVE ANALYSIS 


PHOSPHATE, P0 4 - 

1 . Ammonium Molybdate Test. —Add the reagent to a solution 
of a phosphate acidified with HNO 3 and warmed to 40°, a yellow 
precipitate of (NH 4 ) 3 P0 4 - I 2 M 0 O 3 is formed. Arsenic produces 
a similar precipitate, but a higher temperature is necessary for 
complete precipitation. 

2. Magnesium Mixture, (MgCl 2 +NH 4 Cl+NH 4 OH). —Add 

the reagent to a solution of orthophosphate. The white crystal¬ 
line precipitate is ammonium magnesium phosphate (NH 4 MgP0 4 • 
6 H 2 O). 

Reaction.— MgCl 2 +Na 2 HP0 4 +NH 4 0H = [ NH 4 MgP0 4 +2NaCl+H 2 0. 

The precipitate is soluble in acids, including acetic acid. It 
is slightly soluble in water but insoluble in dilute NH 4 OH. 

Arsenates also gives a precipitate with magnesia mixture. 
The phosphate treated with AgNC> 3 , however, turns yellow, while 
the arsenate changes to a reddish brown color. 

3. Barium Chloride precipitates white BaHP0 4 from neutral 
solutions. The precipitate dissolves in acids (HNO 3 , HC1, 
HC 2 H 3 O 2 ). If NH 4 OH is added to this acid solution Ba 3 (P 0 4 )2 
is precipitated. 

Reactions.— (a) Na 2 HP0 4 +BaCl 2 = i BaHP0 4 +2NaCl. 

(6) BaHPO 4 +2HC1 = BaCl 2 +H 3 PO 4 . 

(c) (3BaCl 2 + 2 H 3 PO 4 ) + 6NH 4 OH = 1 Ba 3 (P0 4 ) 2 +6NH 4 Cl 
+6H 2 0. 

4. Ferric Chloride added to a soluble phosphate slightly acid 
with HC1 precipitates light yellow ferric phosphate. In presence 
of the acid the reaction is reversible. By adding sodium acetate 
the precipitation is complete, since FeP0 4 is insoluble in acetic 
acid. 

Reactions.—(a) Na 2 HP0 4 -f-FeCl 3 = 1 FeP0 4 +2NaCl+HCl. 

(6) Na 2 HP0 4 +FeCl 3 +NaC 2 H 3 0 2 = [ FeP0 4 +3NaCl 
+HC 2 H 3 02. 








THE ACIDS 


197 


The reaction has been considered in the study of the metals 
the Ammonium Sulphide Group. The procedure being used 
r removal of phosphoric acid, which interferes in the detection 
members of this group. 

5. Silver Nitrate precipitates yellow Ag 3 P 04 from neutral 
lutions of orthophosphates soluble in acids and in ammonia. 

2NaHP0 4 +3AgN0 3 = i Ag 3 P 04 +NaH 2 P 0 4 + 3 NaN 0 3 . 

6 . Lead Acetate precipitates white Pbs(P 04 ) 2 , very slightly 
luble in acetic acid, readily soluble in nitric acid. 

2Na 2 HPO 4 +3Pb(C 2 H 3 0 2 )2 = I Pb 3 (P0 4 ) 2 +4NaC 2 H 3 0 2 +2HC 2 H 3 0 2 . 

SULPHATE, S0 4 — 

1. Barium Chloride precipitates white BaSCU from a solution 
staining a sulphate. The heavy precipitate is insoluble in 
lute mineral acids. BaSC >4 is soluble in strong H 2 S0 4 , repre- 
pitated on dilution. 

Reaction.—H 2 SC> 4 +BaCl 2 = I BaS0 4 +2HCl. 

The precipitation is conducted in presence of free nitric or 
fdrochloric acid to prevent precipitation chromates, carbonates 
id sulphites. 

Selenium may be mistaken for sulphur. White BaSe0 4 is precipitated 
Dm the acid (HC1) solution of selenic acid U 2 Se0 4 or its salts. BaSe0 4 
distinguished from BaS0 4 by the fact that boiling it with strong HC1 causes 
3 solution and chlorine gas is evolved, while BaS0 4 is unchanged. 

2 . Lead Acetate precipitates white PbSCU, soluble in 
H 4 C 2 H 3 O 2 , KOH, and in ammonium tartrate. 

Reaction.—H 2 S0 4 +Pb(C 2 H 3 0 2 ) 2 = | PbS0 4 +2HC 2 H 3 0 2 . 

3. Reduction Test. —A sulphate fused with Na 2 C 03 and organic 
lbstance or free carbon (starch, sugar, charcoal, etc.) is reduced 
3 a sulphide. Test for H 2 S by one of the procedures given 
ir this compound on page 167. Other sulphur compounds also 
Drm sulphides. 



198 


QUALITATIVE ANALYSIS 


Analysis of the Barium Chloride Group 

To the neutral solution prepared for acid analysis (Part IV) add BaClj an 
CaClj. If a precipitate does not form, the group is absent. (Silica may t 
present in the original substance, owing to its insolubility. The slight soli 
bility of the calcium and barium borates may prevent the precipitation c 
boric acid.) 

If a precipitation occurs, test for the members individually. Chromate 
are present only in colored solutions. 

In testing for phosphoric acid, make tests first for arsenites and arsenates 
since confusion of interpretation will result, owing to similarity of reactions 
Unless the method of preparation of the solution (Part IV) has removed arseni 
this should be done by passing H 2 S into the acidulated solution (HC1) as Ion 
as a precipitate forms, and filtering off the sulphide. The solution can noi 
be tested for phosphates after first expelling the H 2 S. 

Separation of Arsenates and Arsenites and Phosphates.—To the solutio 
add an excess of magnesia mixture, shake, and allow to stand 5-10 minute: 
filter and wash once. 


Precipitate.—MgNH 4 P0 4 and 

MgNH 4 As0 4 , white. Dissolve the 
precipitate in HC1, heat to boiling and 
pass in H 2 S as long as a precipitate 
forms. (It is advisable to reduce arsenic to arsenous form before passing i 
the H 2 S by boiling with Na 2 S0 3 .) 


Filtrate.—Arsenites. 

Acidify with HC1 and pass in H 2 ‘ 
A copious yellow precipitate is As 2 S 


Precipitate.—As 2 S a or AsiS 3i yellow. 


Filtrate.—PO 4 . Test with amm< 
nium molybdate solution for pho: 
phates. 








THE ACIDS 


199 


CLASSROOM EXERCISES 

1. In the preparation of the acid solution by the addition of Na 2 C0 3 a 
ecipitation generally takes place. Of what general class of substances is it 
>t to be composed? 

2. How can phosphorus or sulphur be detected in an alloy? 

3. Give a method by which BaS0 4 or an insoluble silicate may be rendered 
luble. 

4. In precipitating arsenic acid why is it necessary to acidify with HC1? 

5. Give a method by which a chromate, an oxalate, and a sulphate may be 
parated. 

6. How would you distinguish between: 

(а) A sulphate and a selenate of barium? 

(б) An arsenite and an arsenate? 

(c) A chromic salt, a chromate and a dichromate? 

(d) A sulphate and a sulphite? 

(e) A sulphite and a thiosulphate? 

(/) Magnesium ammonium arsenate and magnesium ammonium 
molybdate? 

(i g ) Fluoride and fluosilicate? 

7. How can you prove the presence of free sulphuric acid in a solution? 

8. How would you test for the acid radical in CaF 2 ? 

9. What is the action between SiF 4 and H 2 0? 

10. Study the Table of Reactions for Inorganic Acids under the column of 
arium Chloride Group, Part V. 



SOLUBLE ACID GROUP 


DESCRIPTIVE 

General Characteristics. 

The members of this group are not precipitated by BaCb no 
by AgN0 3 . 

Individual Characteristics. 

CHLORIC ACID, HCIO, 

Only the aqueous solution containing 40 per cent of HC10 3 is knowr 
It is a thick colorless liquid which readily decomposes into Cl+O and pei 
chloric acid, HCIO 4 . It is a very active oxidizing agent. Chlorates readil; 
give off the oxygen, decomposing with explosive violence when rubbed o 
heated with oxidizable bodies, such as P, S, SbS, sugar, etc. All chlorate 
are soluble in water. With prolonged ignition chlorates are decompose' 
liberating oxygen and leaving a residue of the chloride salt. 

Detection of Chlorate.—The dry salt heated with concentrated sulphuri 
acid detonates and evolves yellow fumes. 

Chlorates liberate chlorine from hydrochloric acid. 

Perchlorate.—The solution is boiled with hydrochloric acid to decompos 
the hypochlorite, chlorite and chlorate. The Chlorides is removed by precip 
itation with silver nitrate, the filtrate evaporated to dryness, the residue fuse< 
with sodium carbonate to decompose the perchlorate to form the chloride 
which may now be tested as usual. 

See tests under Laboratory Exercises, page 203. 

NITROGEN 

Element, N 2 , at.wt. 14.01; D. (air) 0.9674; m.p. —210°; b.p. —195.6® C. 

oxides, N 2 0, N 2 0 2 , N 2 O s , N 2 0 4 , N 2 O s . 

Occurrence. Element.—It occurs free in air to extent of 78 per cent b 
volume and 76 percent by weight. 

Nitrogen is found combined in nature as potassium nitrate (saltpeter' 
KN0 3 ; sodium nitrate (Chili saltpeter), NaN0 3 , and to a less extent a 
calcium nitrate, Ca(N0 3 ) 2 . It occurs in plants and in animals, in the sut 

200 


THE ACIDS 


201 


ances proteids, blood, muscle, nerve substance, in fossil plants (coal), in 
lano, ammonia and ammonium salts. 

Compounds of ammonia and of nitric acid are generally soluble in water. 
11 nitrogen compounds, however, are not included. Among those which 
•e not readily soluble the following deserve mention: compounds of nitrogen 
many organic substances; nitrogen bromophosphide, NPBr 2 ; nitrogen 
lenide, NSe; nitrogen sulphide, N 4 S 4 ; nitrogen pentasulphide, N 2 S 6 ; 
nmonium antimonate, NH 4 Sb0 3 -2H 2 0; ammonium iodate, HNJO 3 
!6 grams per 100 cc. H 2 0); ammonium chlorplatinate, (NH 4 ) 2 PtCl 6 (0.67 
•am); ammonium chloriridate, (NH 4 ) 2 IrCl e (0.7 gram); ammonium oxalate, 
^H 4 ) 2 C 2 0 4 -H 2 0 (4.2 grams); ammonium phosphomolybdate, (NH 4 ) 3 PU 4 - 
2Mo0 3 (0.03 gram); nitron nitrate, C 2 oHi 6 N 4 -HN0 3 . 

DETECTION 

Element. Organic Nitrogen.—Organic matter is decomposed by heating 
L a Kjeldahl flask with concentrated sulphuric acid whereupon ammonium 
jilphate is formed. Ammonia may now be liberated from the sulphate and so 

31 Nitrogen in Gas.— Recognized by its inertness towards the reagents used 
1 gas analysis. The element may be recognized by means of the spectroscope. 


NITRIC ACID 


IINOs, m.w., 63.02; sp.gr. 1.53; m.p. -41.3; b.p. 86° C. 

Boiling-point of commercial 95 per cent acid is a little above 86°, but gradu- 
ly rises to 126° and the strength of acid falls to 68.9 per cent, sp.gr is then 
42 The acid now remains constant, the distillate being of t e same s reng 1 . 

The acid radical occurs in nature in the for *1 of 
hili saltpeter NaN0 3 ; potassium nitrate, KN0 3 ; and Ca(N0 3 ) 2 , wa 
iltpeter Nitrates are formed in all decomposition processes o organic 
itrogenous substances. Nitrates are all soluble in water, except a few basic 
itrates such as BiONOs, etc. Most nitrates are deliquescent, except those 
f Ag, Pb, Sr, Ba, Na, K, NH,. Boiling with sodium carbonate forms sodium 

itrate. 


detection of nitric acid and nitrates 

Nitrates are detected by the brown color produced by the action of a 
touted sulphuric acid solution of ferrous sulphate on a nitrate solu ion 

irongly acid with H 2 S0 4 . 

With diphenylamine reagent nitrates give a bue c 
See tests under Laboratory Exercises, page 20d. 




202 


QUALITATIVE ANALYSIS 


For detection of nitrous acid and nitrites, see subject under the Volatil 
Acid Group, pages 159, 165. 

PERMANGANIC ACID, HMn0 4 

This acid is known only in its aqueous solutions and in the form of it 
salts, i.e., KMn0 4 , NaMn0 4 , etc. The permanganates are all soluble in water 
forming purple solutions. Like the chlorates, they are good oxidizing agents 
They liberate chlorine from hydrochloric acid and oxidize ferrous salts t< 
ferric, sulphur dioxide to sulphuric acid, oxalic acid to CO 2 and H 2 O. 

Reaction, Acid Solution.—2KMn0 4 +3H 2 S0 4 in presence of reducin 
agent = K 2 S0 4 +2MnS0 4 +3H 2 0+50. 

Alkali Solution.—2KMn0 4 +H 2 0 = 2Mn0 2 +2K0H+30. 

Detection.—Permanganate solutions are pink or red according to th 
concentration of the solutions. 

Permanganates are reduced by H 2 S to manganous salts. The tests fo 
manganese have been given in Part II under the Ammonium Sulphide Group 
pages 88 and 103. 






THE ACIDS 


203 


LABORATORY EXERCISES 

Reactions—Characteristic Tests 
CHLORATE, C10 3 - 

1. Sulphuric Acid, concentrated, decomposes chlorates with lib- 
ration of CIO 2 greenish-yellow gas. The unstable CIO2 decom- 
oses on warming. This is evident by the fact that when strong 
[ 2 SO 4 is added to the dry salts an explosion results, with slight 
^arming of the mixture. Make the test by placing strong H2SO4 
1 a test tube, drop in a crystal of KCIO3 and warm gently over a 
)w flame. 

Reaction.—3KC10 3 +2H 2 S0 4 = T 2 C 10 2 +KC 10 4 + 2 KHS 04 +H 2 0 . 

2. Oxidizing Action. —Chlorates react with strong HC 1 liberat- 
ig CIO 2 and Cl and forming a chloride. 

Reaction.—KC10 3 -|-2HC1 = t CIO 2 + t Cl-f-KCl-fHjO. 

3. Reducing Agents. —Add an alkali sulphite to a chlorate 
lolution and acidify with H2SO4. The SO2 reduces the chlorate 

o a chloride. 

HCIO 3 +3SO 2 +3H 2 0 = 3H 2 SO 4 +HC1. 

4. Aniline Sulphate Test.— To a solution of chlorate in cold 
■one. H2SO4 add a drop of aniline sulphate. A deep blue color is 
leveloped. The color becomes more intense by adding a few 
Irops of water. 

NITRATE, N0 3 - 

1. (a) Ferrous Sulphate Test— When concentrated nitric acid 
s added to a solution of ferrous sulphate, the ferrous salt is oxidized 
bo Fe 2 (SC> 4)3 and NO is formed. The oxide of nitrogen unites 
with the unchanged ferrous sulphate, forming a brown unstable 
compound (FeS 04 ) 2 N 0 . 

About 1-2 cc. of the concentrated solution of the substance 
is added to 15 to 20 cc. of strong sulphuric acid in a test tube. 




204 


QUALITATIVE ANALYSIS 


After cooling the mixture, the test tube is inclined and an equj 
volume of a saturated solution of ferrous sulphate is allowed t 
flow slowly down over the surface of the acid. The tube is no 1 
held upright and gently tapped. In the presence of nitric acid 
brown ring forms at the junction of the two solutions. 

(6) A nitrate may be tested by adding to the solution sufficiec 
sulphuric acid to make it strongly acid and then a large excess c 
a saturated solution of ferrous sulphate and sulphuric acid. 1 
pink to brown color is obtained, depending upon the amount c 
nitrate present. A quantitative method has been worked ou 
from this test. The brown color is permanent when an exces 
of the ferrous salt is present, since free nitric acid fades th 
color. 

Reaction.—2HN0 3 +3HS0 4 +6FeS0 4 = 2NO +3Fe 2 (S0 4 ) 3 +4H 2 0 
and NO+2FeS0 4 = (FeS0 4 ) 2 N0 brown. 

Interfering Substances.—Nitrites give the same test as (a). These d 
not interfere in test ( b ) if present in comparatively small amount. 

Iodides and bromides are liberated by concentrated H 2 S0 4 . These ma 
be removed by adding a solution of Ag2S0 4 or AgC 2 H 3 0 2 and filtering 
The filtrate contains the nitrate; the residue is AgBr and Agl. 

Ferrocyanides and ferricyanides form blue compounds with FeS0 4 , whic 
mask the brown ring. They may be removed by adding H 2 S0 4 to acidit 
and then FeCl 3 and FeSOi, heating to boiling and adding BaCl 2 . Th 
residue contains the cyanides and BaS0 4 . Test the filtrate for nitrates. 

Chromates , permanganates , and chlorates interfere, the first two o 
account of their color, the latter because of the violent action that take 
place when concentrated sulphuric acid is added. They may be remove 
as follows: add Na 2 S0 3 in a porcelain dish and introduce a small portio 
of the original substance and add dilute HC1, warm gently until all exces 
of H 2 S is expelled, filter, and reject the residue. If the filtrate is sti 
colored, add Na 2 C0 3 until effervescence ceases, boil 2-3 minutes, dilute an 
filter. The filtrate is used for the nitrate tests. 

2. Phenol Sulphonic Acid Test for HNO 3 . —Evaporate a fe^ 
drops of the solution (freed from chromates, permanganates 
chlorates, and ferro and ferricyanides) to dryness in a porcelai 


THE ACIDS 


205 


crucible, cool the residue, and add 2-3 cc. of the reagent 1 and 
warm gently; now add NH 4 OH. The deep yellow ammonium 
picrate is formed if nitrates are present. Iodine and bromine 
do not interfere with this test. This method is used in water 
analysis in quantitative tests for nitrates. 

3. (a) Reduction Test. —Dissolve in the solution a small 
crystal of KI and then add a drop of starch solution and 2 cc. of 
dilute H 2 SO 4 and a small piece of zinc. If nitrates are present, a 
blue color will result, first appearing around the zinc. 

The H liberated reduces HN0 3 to HN0 2 , and the latter 
liberates free I, causing the starch to be colored. CS 2 may be 
used in place of the starch. Further reduction will liberate 
ammonia which can be recognized by its odor. See ( b ). 

(6) Reduction to Ammonia. —Make the nitrate solution 
strongly alkaline with NaOH and add metallic filings of aluminum, 
or zinc or iron and heat. Note the odor of NH3 due to the reduc¬ 
tion of HNO3. Nitrites also are reduced to NH3. 

4. Diphenylamine Test. —To 2 cc. of the solution containing the 
| nitrate, placed on a watch glass, add 5 cc. of the reagent made by 

dissolving 5 mg. of diphenylamine, (C 6 H 5 )2NH, in 100 cc. of cone. 
H2SO4 Warm gently. A blue color develops in presence of 
nitrates. Cl, Cl v , Br v , I v , Mn VI1 , Cr VI , Se IV , and Fe"" interfere. 

5. Free HN0 3 — (a) Copper filings placed m a hot solution of 
HNO3 cause the evolution of brown fumes. 

3Cu+8HN0 a +0 2 (air) = T 2N0 2 +3Cu(N0 3 ) 2 +4H 2 0. 

(6) The solution evaporated to dryness with addition of a 
quill cutting will color the quill yellow. (Xanthoproteic acid is 
formed.) 

PERMANGANATE, Mn0 4 _ 

1 A permanganate colors a solution red. It may be made 
colorless by reduction to Mn0 2 in an alkaline solution and to 

■ Reagent contains 1 part phenol (cryst. carbolic acid), 4 parts strong 
I H 2 S0 4 and 2 parts H 2 0. 



206 


QUALITATIVE ANALYSIS 


manganous salt in an acid solution by reducing agents such as: 
H 2 S, FeS0 4 , H2C2O4, S0 2 . 

Hydrogen peroxide decolorizes a permanganate, acidified with 
sulphuric acid, with the evolution of oxygen. 

See section on Manganese under the members of the Ammo¬ 
nium Sulphide Group, Part II on Metals, page 88, 103. 

Analysis of the Soluble Acid Group 

If the solution is colored red, a permanganate is indicated. Decolorize by 
adding H 2 0 2 . 

Evaporate a portion of the solution on the water bath to dryness and test 
the residue for chlorate. 

If a chlorate is present, to a second portion add sodium sulphite (to 
reduce the chlorate) and boil. Cool and test for nitric acid. 

CLASSROOM REVIEW 

1. What is the effect of concentrated sulphuric acid on a chlorate? 

2. What is the effect of hydrochloric acid on a permanganate? 

3. How can you distinguish free nitric acid from a solution of its salt? 

4. Devise a method for separating the acid radicals: C0 3 —, 1“ and 
NO3-. 

5. (a) How can you distinguish between nitrates and nitrites? 

(6) In the catalytic oxidation of ammonia to nitric acid both nitric 
acid and nitrous acid are present in the dilute aqueous solution. How can 
you detect the latter in presence of the former? 



ORGANIC ACID GROUP 
DESCRIPTIVE 

General Characteristics. 

The acids of this group (except oxalic acid) char when heated 
to redness. All organic acids contain the carboxyl groups 
COOH~. The number of these carboxyl groups determines the 
valency of the acid,—monobasic acetic acid, H+CHsCOO - ; 
/COO 

x coo 

plex radical, the acids dissociate into H — R (COO). The potas¬ 
sium and sodium salts of nearly all organic acids are soluble. 
Organic acids occur free or combined as salts of the alkalies and 
other metals together with inorganic salts. Tests should be made 
with the alkali salts or by neutralizing the free acids with an alkali 
carbonate. Only a few of the acids will be studied here. A list 
of additional organic acids and their tests is given in Part V. 

Individual Characteristics. 


dibasic oxalic acid 2 H 


Letting R represent the com- 


ACETIC ACID 

HC 2 H 3 O 2 .— Mol.wt. 60.03; sp.gr. 1.06; m.p. 17°; b.p. 118°. This acid 
occurs in both the animal and the plant kingdoms, free and also combined. 
When not free it is found as calcium or potassium acetate. In pure form at a 
temperature below 17° it forms a clear colorless mass. It produces blisters 
on the skin. It dissolves many organic substances, also S and P. Acetates 
are readily soluble in water, except those of Ag, Hg, and certain basic salts. 
On heating they decompose and leave a residue. The hydroxides of certain 
metals are precipitated when their acetates are boiled. Acetates are trans¬ 
posed by boiling with Na 2 C0 3 . 

On heating acetates decompose with the production of a combustible gas 
and practically no charring. 


207 



208 


QUALITATIVE ANALYSIS 


OXALIC ACID 

H 2 C 2 0 4 -2H 2 0. —Mol.wt. 126.05; sp.gr. 1.65; m.p. 98°. Readily soluble 
in alcohol. Most oxalates, except those of the alkalies, and Mg, are not 
readily soluble in water, but soluble in mineral acids. They form sodium 
salts when boiled with Na 2 C0 3 . Oxalates occur in both animal and plant 
kingdoms. 

On heating oxalates are decomposed with evolution of CO and C0 2 . 
Oxalates of the alkaline earths and alkalies are decomposed to carbonates. 
Little or no charring occurs. Magnesium oxalate yields MgO on heating. 
Other oxalates leave a residue of the metal or an oxide. 

SALICYLIC ACID 

H 2 C 7 H 4 03 .—Mol.wt. 138.05; m.p. 159°; b.p. sublimes. Colorless 
needle-shaped crystals, odorless. Very slightly soluble in water; readily 
soluble in ether and alcohol. Soluble in sodium carbonate. Most of the salts 
of the acid are soluble in water. These are decomposed by dilute mineral 
acids, the salicylic separating out as a white crystalline precipitate. 

TARTARIC ACID 

H 2 C 4 H 4 06.—Mol.wt. 150; sp.gr. 1.667; m.p. 1.40°. Rectangular crystals. 
It forms acid and neutral salts, being dibasic. The normal salts with the 
alkalies and most of the salts with the metals of the iron group are readily 
soluble in water. Other normal salts are mostly insoluble. The acid salts 
of potassium and ammonium are difficultly soluble. Tartrates char on heat¬ 
ing. Inflammable vapors are evolved, having an odor of burning sugar. 


THE ACIDS 


209 


LABORATORY EXERCISES 

i Reactions—Characteristic Tests 

The student is referred to the Tables of Reactions for tests of 
Organic Acids, Part V, for additional exercises in the study of this 
*roup. 

ACETATE, C 2 H 3 0 2 - 

1. Sulphuric Acid Test.—Acetic acid is liberated from its salts 
svhen warmed with cone. H2SO4. It can be recognized by its 
Ddor (vinegar). A little alcohol added forms ethyl acetate, 
C 2 H 5 (C 2 H 302 ), which has a characteristic pleasant odor. 

2. Ferric chloride added to a neutral solution of an acetate 
forms a deep red color. If this solution is diluted and boiled, 
Fe(OH ) 2 • C 2 H 3 O 2 , red, is precipitated, leaving a clear liquid above. 

OXALATE, C2O4 — 

1. Calcium sulphate solution added to an oxalate solution 
acidified with acetic acid will precipitate white CaC 2 04- 

Further Confirmation. —Filter, wash and dissolve in a little 
dilute sulphuric acid and add a drop of KMn0 4 . If the perman¬ 
ganate is decolorized, it is due to the reducing action of the oxalate. 

SALICYLATE, C7H4O3 

1. Ferric chloride produces an intense violet-red color with 
both salicylic acid and salicylates. This color is destroyed by 
excess of mineral acids and by a large excess of most organic 
acids, but is restored by neutralizing the acid with ammonia. 

2. Nitric acid (cone.) when heated with salicylic acid or its 
salts forms picric acid, yellow: the yellow color is intensified by 
addition of an excess of NaOH. 

TARTRATE, C 4 H 4 0 6 

1. Sulphuric acid, cone., causes an effervescence, when added 
to a tartrate and gives off an odor of burnt sugar. The acid is 
darkened due to charring. 



210 


QUALITATIVE ANALYSIS 




2. Silver Nitrate, in faintly ammoniacal solution, heated in a 
clean test tube with a tartrate, is reduced to metallic silver, which 
forms a mirror on the glass. 


Analysis of the Organic Acids 


Test a portion for oxalates by adding CaSOi. A precipitate indicates an 
oxalate. The precipitate should be soluble in acetic acid without the evolution 


of C0 3 . 

Evaporate almost to dryness. If an oxidizing agent is present, reduce by 
means of S0 2 or H 2 S during the evaporation. Test a portion of the concen¬ 
trated solution for acetic acid. Test another portion for tartaric acid. 


CLASSROOM EXERCISES 

1. State the uses made of the three acids studied in this group. 

2. Give a scheme of analysis leading to the detection of the following i 
present in a solution: sulphite, arsenite, thiosulphite, sulphate, bromide, iodide, 
ferrocyanide, acetate. 

3. How would you detect a chloride in the presence of a sulphide? 

4. How would you detect a nitrate in the presence of a ferricyanide? 

5. How would you distinguish an organic acid from an inorganic acid? 

STUDIES OF REACTION LIMITS 

This is a study of typical reactions to ascertain approximately 
the conditions and concentration necessary for a given substance 
in order to obtain a discernible test of its anion or cation. The 
student should take a normal solution of the substance and dilute 
portions to * N, 5^ N, tJo N, N, 5^ N, refer N. To these 
solutions, in separate test tubes, add, drop by drop, the precipi¬ 
tating reagent, the strength of which is known. Determine the 
dilution limit at which the ion may be recognized. Does heating 
render the reaction more or less delicate? Calculate the approxi¬ 
mate amount of salt necessary in a hundred cc. of the solution to 
enable the detection of its ions. 




PART IV 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 

Preliminary Examination of a Solid 

Physical Examination and Dry Tests of the Solids.— Object .— 
V preliminary examination is made in order to gain some knowl¬ 
edge of the character of the substance before putting it into 
iolution. The process of analysis is frequently shortened by the 
)hysical examination of the solid and by a few preliminary chemi¬ 
cal tests. The appearance, crystalline form and color of the solid 
iubstance, changes on exposure to the air, chemical changes due 
,o decomposition when heated or treated with certain reagents, 
>xides formed causing color changes, or the color and odor of 
leases evolved, color of oxide with the borax bead, flame tests, 
•eduction tests on charcoal, etc., give valuable indications of a 
lumber of compounds and elements. 

Certain substances, furthermore, must be tested for in the 
iriginal substance—for example, ammonia. Then, again, since 
ixidizing and reducing agents are used during the course of 
imalysis, metals having two valences will undergo a change, so 
diat in order to find out in what form they exist in the substance 
t is necessary to examine the original compound by special tests. 

In making an analysis, the chemist should bear in mind the 
imount of substance he has at his disposal, and leave a part of the 
naterial for confirmatory tests. His success will depend upon a 
dextrous and cleanly performance of the operations necessary in 
the chemical analysis. 

Procedure .—Spread out the substance on a sheet of glazed 
paper, and observe whether it is an alloy or a compound; hetero¬ 
geneous or homogeneous. If the substance is in a powdeied form, 

211 



212 


QUALITATIVE ANALYSIS 


examine it under a pocket lens and observe the color and form 
of the characteristic particles. Is the compound efflorescent oi 
deliquescent upon standing exposed to the air? Has it an odor? 
The constituents of a mixture can often be recognized by the 
physical examination. 

The color of substances may give a clue to its composi¬ 
tion. 

Many of the oxides of metals are black; cobalt salts are gen¬ 
erally of a reddish hue when moist, and blue in the desiccated 
form: manganese salts are mostly pink; mercury, reddish yellow; 
nickel, green; copper, green and blue; chromium, green, yellow, 
red, and violet; gold, yellow. The halogens, combined with the 
alkaline earths and the alkalies, are white; chromates color 
solutions yellow,, permanganates, dark red color. Regarding 
the color of the elements, many of the elements appear gray in 
powdered form, and in lumps possess a silver-white lustre when 
freshly cut. The halogens vary in color: fluorine, greenish yel¬ 
low; chlorine, yellow; bromine, dark red; iodine, purplish black. 
Silicon appears in its pure form as a black powder; boron, shining 
greenish black crystals; arsenic, black; caesium, gold, and copper 
have a yellow metallic lustre, deepening into a reddish yellow 
in the order named. Sulphur and phosphorus are translucent 
pale-yellow substances. A very large number of compounds exist 
that appear white in the powdered form; a physical examination 
of these offers but little clew to an amateur. 

Preliminary Chemical Examination. Dry Tests. 

Solid substances may be divided into two classes: 

(a) Metals or alloys. 

(b) Compounds or substances containing metals and non- 
metals, or acid radicals. 

(a) The first generally possess metallic lustre when freshly cut; 
they are malleable; a few are brittle. They all possess high 
specific gravity. 


[■' JxfD 

SYSTEMATIC ANALYSIS OF A SUBSTANCE 213 


(b) The second class usually lack metallic lustre and are more 
r less brittle and can be easily reduced to a powder. In solution 
hey ionize. 

The preliminary tests will be taken up in the following order: 

A. Combustion Tube Test. 

B. Reduction or Charcoal Test. 

C. Flame Test, including spectra of the flame. 

D. Borax Bead Test. 

E. Sulphuric Acid Test. 

The first four apply to metals and the last to acids. 

A. Combustion Tube Tests 

Results of Tests 

’he substance chars 
’he substance swells 

"he substance melts and water is evolved. 

Inferences 

Organic matter. 

Borates,alums, Hg(CNS) 2 . 
Alkali salts, oxides, water 
of crystallization. 

Tie substance changes color. 

(a) Change of color due to oxides . 

APPEARANCE cold appearance hot 

White Yellow, unfused 

Light yellow Yellowish brown, unfused 
Yellow Yellowish red, fuses 

Pale yellow Orange, fuses 

Yellow Dark orange, fuses in high heat 

Brownish red Dark red to brown, unfused 
Red Black, fuses yellow 

Red Black, globules of Hg sublimes 

on heating 

ZnO. 

Sn0 2 . 

PbO. 

Bi 2 03. 

PbCr0 4 . 

Fe 2 0 3 . 

Pb 3 0 4 . 

HgO. 

(b) Change of color due to dehydration. 

HYDRATED SALT DEHYDRATED SALT 

Green or blue White or pale green 

Green Cray or yellowish 

p in k Blue or violet 

Copper salts. 

Nickel or iron salts. 

Cobalt salts. 



















214 


QUALITATIVE ANALYSIS 


A. Combustion Tube Tests —Continued 


(c) Change of color due to decomposition. 

ORIGINAL SUBSTANCE RESIDUE 

Colorless Red 

Hg(N0 3 ) 2 

Colorless 

Yellow 

or HgN0 3 , HgC 
Pb(N0 3 ) 2 , PbO. 

White 

Yellow 

Pb(C0 3 ) 2 , PbO. 

Green 

Black 

Ni(N0 3 ) 2 , Ni 2 0 3 . 

Green 

Red 

FeS0 4 , Fe 2 0 3 . 

Light green 

Black 

CuC0 3 , CuO. 

Blue 

Black 

Cu(N0 3 ) 2 , CuO. 


The substance evolves gas. 

(a) Gas is colored , and may have an odor. 


Brownish red, stifling odor 


Greenish yellow, suffocating 
Violet, acrid odor 
White fumes 


Oxides of nitrogen du 
to nitrates on nitrites 
Chromyl chloride due t 
chromates and chic 
rine. 

Bromine compounds. 
Chlorine from Au, Pt, Cr 
Iodine compounds. 
Steam. Water of crystal 
lization, S0 3 , sulphate 
HC1 from chlorides. 


(b) Gas is colorless , odorless and may burn. 
Kindles a glowing chip of wood 


Kindles a glowing chip of wood and evolves 
steam 

Burns with a blue flame 


Oxygen from oxides, pei 
oxides, nitrates, chrc 
mates, chlorates, etc. 

Nitrous oxidefroD 
NH 4 NO 3 . 

CO from organic com 
pounds, oxalates, etc. 


Does not burn, makes a drop of limewater on 
a glass rod turbid 


CO 2 from carbonates. 









SYSTEMATIC ANALYSIS OF A SUBSTANCE 


215 


A. Combustion Tube Tests —Continued 


(c) Gas colorless, and has an odor. 

Odor of ammonia, turns red litmus blue 

Odor of burning sulphur 

(d) Poisonous gases with odor and will burn. 
Burns with purple flame, odor of peach blos¬ 
soms or bitter almonds 

Burns with blue flame, odor of rotten eggs, 
blackens lead acetate 

Burns with green flame, odor of rotten fish 
Burns with lilac flame, odor of garlic 

NH 3 from salts or organic 
matter. 

SO 2 from thiosulphates, 
sulphites, sulphates, 

sulphides. 

C 2 N 2 from cyanides of 
heavy metals. 

H 2 S from sulphides. 

PH 3 from hypophosphates. 

AsH 3 from certain arsenic 
compounds. 

The substance gives a sublimate • 

White sublimate. 


Soluble in water 

NH 4 CI, HgCl 2 , HgBr 2 . 

Insoluble in water 

HgCl, HgBr. 

Needle-shaped crystals 

Sb 2 0 3 . 

Octahedral crystals 

As 2 0 3 . 

Organic compounds 

Oxalic acid, benzoic acid. 

Black sublimate. 

As, Sb. 

From metals, or by reduction 

Violet vapors (brown in alcohol) 

Iodine. 

Gray mirror of glistening globules 

Mercury. 

Becomes red on rubbing 

HgS. 

Reddish brown sublimate. 

Sulphur. 

Brownish drops, yellow on cooling 

Brownish red, yellow on cooling 

AS 2 S 3 . 

Dark red, orange on cooling 

Sb 2 S 3 . 

Yellow, turns red when rubbed 

Hgl 2 . 














216 


QUALITATIVE ANALYSIS 


B. Blowpipe Tests on Charcoal 

Heat a small portion of the material on charcoal in the reducing flame, 
using a blowpipe. Scoop out a round hole in the charcoal, place a little of the 
substance in the cavity, and direct the inner flame of the blowpipe against 


it at an angle of thirty degrees. 


Result of Test 

Inference 

Melts and runs into the charcoal 

Alkalies, K, Na, etc. 

An alkaline residue on charcoal 

Ca, Sr, Ba, Mg. 

A residue which, when moistened with a drop of 
Co(N 0 3 )3 and heated in 0. F., produces a color 


which is blue 

Aluminum, silicon. 

Produces a color which is green 

Zinc, tin, antimony. 

Produces a color which is red 

Barium. 

Produces a color which is pink, or rose-red 

Manganese. 

Deflagrates 

Nitrates, chlorates. 

Leaves an incrustation which is white near flame 

Antimony. 

White, garlic odor 

Arsenic. 

Dark red 

.Silver. 

Red to orange 

Cadmium. 

Lemon yellow (hot), light yellow (cold) 

Lead. 

Orange yellow (hot), light yellow (cold) 

Bismuth. 

Yellow (hot), white (cold) 

Zinc or tin, latter non¬ 
volatile. 

Blowpipe Tests.—Substance fused with Na 2 C0 3 on Charcoal. Place a 

small amount of the substance on charcoal with a little sodium carbonate and 

fuse, using reducing flame. 

Result of Test 

Inference 

Metallic globules, without incrustation 


Yellow flakes 

Gold. 

Red flakes 

Copper. 

White globule, moderately soft 

Silver. 

Metallic globules, with incrustation 


White, moderately soft beads 

Lead or tin (volatilized 
lead leaves yellow coat). 

White, brittle beads 

Bismuth or antimony (yel¬ 
lowish). 

Yellow in 0. F. 

Chromium. 

Green in 0. F. 

Manganese. 

A substance (in R.F.) which, when moistened and 
placed on a silver coin, leaves a brown or black 


stain 

Sulphur compounds. 














I 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 


217 


B. Blowpipe Tests on Charcoal —Continued 


Test 


Inference 


! Dark gray magnetic powder, which, when moistened 
on a filter paper with a drop of dil.HCl and NHO-s, 
and gently dried over a flame, leaves a stain which 
is faint pink, turning blue 
Green stain, turning yellow 
A stain turned blue by K 4 Fe(CN ) 6 


Cobalt. 

Nickel. 

Iron. 


In place of using charcoal the above tests may be made with a splinter of 
wood covered with a coating of fused Na 2 C0 3 . The test is made by dipping 
the heated splinter into a mixture of the powdered substance with fused sodium 
carbonate and plunging for a moment in the reducing flame. Examine the 
material on the splinter, scrape off on a piece of glazed paper and examine. 

Blowpipe Tests.—Substance moistened with cobalt nitrate solution and 


i ignited. 


Color of Residue or Incrustation 

Inference 

Brick red 

BaO. 

Pink 

MgO. 

Gray 

SrO, CaO. 

Yellowish green 

ZnO. 

Dark muddy green 

Sb 2O5. 

Bluish green 

SnO. 

Blue 

AI2O3, Si02. 


C. Flame Test 

Moisten a clean platinum wire in strong HC1, dip into the powdered sub¬ 
stance and insert into a Bunsen flame. If sodium is present examine through 
a blue glass. (Test the cobalt glass to see if it is effective in cutting out t 
yellow sodium light by examining a sodium flame through it.) 

Flame Color. Color through Blue Glass- Element. 


Carmine red 

Dull red 

Crimson 

Golden yellow 

Greenish yellow 

Green 

Blue 

Violet 


Purple 
Olive green 
Purple 
Absorbed 
Bluish green 


Violet red 


Lithium 

Calcium 

Strontium 

Sodium 

Barium, molybdenum 
Cu, — PO 4 , — B 2 O 3 

Cu, Bi, Pb, Cd, Zn, Sb, As 
Potassium 

















218 


QUALITATIVE ANALYSIS 


The platinum wire should be cleaned before making the test. This can be 
accomplished by dipping it into cone. HC1 and holding it in the Bunsen, or 
better, a flame of a blast lamp, until the flame is no longer colored. Repeat¬ 
edly dipping into the HC1 may be necessary. 

Examine the flame through a spectroscope, if available, and compare the 
spectra with a spectra chart. Mere traces of the alkali and alkaline earth 
metals can be detected in this way by their characteristic spectral lines. 


D. Behavior of Substances fused with Microcosmic Salt and Borax Beads 

A clear bead is formed by fusing the flux on a loop of platinum wire. Dip the bead, in the finely powdered substance 
to be examined, and heat again—first in the oxidizing flame; second in the reducing or inner flame. Metallic salts 
are mostly changed to oxides. In the Table— h. signifies hot; c ., cold; sups., supersaturated with oxide; s. s., 
strongly saturated; h. c., hot and cold. 


F 

SYSTEMATIC ANALYSIS OF A SUBSTANCE 219 



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220 


QUALITATIVE ANALYSIS 


E. Sulphuric Acid Tests. The Acids 

Sulphuric acid volatilizes a number of acids, some of which can be posi¬ 
tively identified by their odor or color. 

Method. —Place a small portion of the solid in a test tube, add a few drops 
of cone. H 2 S0 4 , and observe results; now heat cautiously, but do not boil. 
Note the color of the gases evolved, and by holding the test tube at a slight 
distance and fanning the fumes with the hand toward the nose, gradually 
bringing the test tube nearer, note the odor of the gases. 


Result of H 2 S0 4 Test 

Colorless gases with or without odor generally 
effervescent. 

Inference 

Material turns black, odor of burnt sugar 

C 2 H 4 O 6 , tartrates. 

Odor of vinegar or acetic acid 

No odor, makes turbid a drop of lime water on a 

C 2 H 3 O 2 , acetates. 

glass rod 

C0 2 , carbonate or oxalate. 

No odor, burns with a blue flame 

No odor, with addition of alcohol burns with 

CO, oxalate or ferrocyanide. 

green flame 

B 2 O 3 , borate. 

Odor of rotten eggs, blue flame, blackens lead 

H 2 S, sulphide or sulphite 

acetate paper 

Odor of burning sulphur, blackens paper mois¬ 

+reducing agent. 

tened with HgN0 3 

SO 2 , sulphite. 

Same as above—free sulphur pptd. 

SO 2 , from S 2 0 3 , thiosulphate 

Corrodes the test tube 

HF, fluorides. 

Odor of HC1, white fumes with NH 4 OH on rod 
Colorless, having an odor of bitter almonds or 

HC1, chlorides. 

peach blossoms, extremely poisonous vapor 
Colored gases with odor. 

C 2 N 2 , cyanide, ferrocyanide. 

Yellowish, pungent odor 

Cl, hypochlorite, chlorate -f- 
reducing agent, chloride -J- 
oxidizer. 

Yellowish green, suffocating, explosive 

C10 2 , chlorate. 

Brownish red, stifling odor 

HBr, Br, bromides. 

Brown or deep red vapor, suffocating 

Violet vapor, acrid odor, separation of black 

NO 2 from nitrites or nitrates 

powder 

Precipitate formed. 

I, iodides. 

White precipitate, flocculent 

H 2 Si0 3 , silicates. 






SYSTEMATIC ANALYSIS OF A SUBSTANCE 


221 


PRELIMINARY EXAMINATION OF A LIQUID 

If the material is a liquid test this with litmus paper; if neutral, 
jvaporate a few drops on a platinum foil over the flame, or on a 
vatch glass (on a water bath) if volatile products are suspected, 
[f there is no residue left, the substance is pure water. 

If the solution is acid, either free acid is present or an acid 
salt, such as sodium hydrogen sulphate, or alum. 

If the solution is alkaline, the substance may contain free 
ilkali or the alkali salt of a weak acid. 


ANALYSIS OF THE METALS 

The preliminary examination of the solid often affords positive 
indications of its composition; for a more extended examination, 
however, it is necessary to get the substance into solution and to 
test for its components by liquid reagents. 

Before this can be done certain interfering substances must 
be removed. We learned in our study of the metals of the Ammo¬ 
nium Sulphide Group that organic matter interfered in precipita¬ 
tion of certain metals. Oxalic and phosphoric acids caused 
precipitation of metals of succeeding groups. Provision must be 
made against such interference by removal of the substances in 

question. . 

Organic Matter.—The charring of the substance by heating 
in the preliminary test and the odor have indicated the presence 
of organic matter. This may be removed by combustion at 
red or white heat, but this would cause volatilization of certain 
substances such as ammonia, mercury, arsenous, and antimonous 
compounds. An effective procedure is by oxidation of organic 
matter either by heating it with strong HC1 and adding KClOs 
crystals or by adding strong HNOs followed by concentrated 
H2SO4 and heating to fumes, preferably in a round-bottom flask. 
The heating being continued until the solution changed from a 



222 


QUALITATIVE ANALYSIS 


black tarry mass to a straw-colored solution. Should the hydro¬ 
chloric acid procedure be employed the metals would be in form 
of chlorides while the last method would form sulphates. 

Oxalic Acid.—This is destroyed by the procedure used for 
removal of organic matter. 

Phosphoric Acid.—Reference is made to the notes on the 
metals of the Ammonium Sulphide Group for the detection of 
phosphoric acid and the procedure and for its removal, page 115. 

Preparation of the Solution for Detection of the Metals 

I. SUBSTANCES SOLUBLE IN WATER. 

Salts and Oxides .—Water as a Solvent .—To about one gram of the well- 
mixed substance, pulverized in a mortar (test small portion for explosives, etc. 
KC10 3 ) and placed in a large test tube, add about 10-20 cc. of distilled water; 
boil for 10 minutes; allow to settle if any residue remains. Test with litmus 
paper. If solution is neutral or acid, filter. Add more water to any residue 
that may remain; boil and filter, combining filtrates. If considerable residue 
remains evaporate a portion of the extract to dryness and observe whether a 
residue remains. The material in solution is examined by the standard scheme 
for analysis. Water insoluble material is treated as directed below. 

II. SUBSTANCES INSOLUBLE IN WATER AND SOLUBLE IN ACIDS 

Should the substance not dissolve in water it must be treated by the Add 
Solvents. If the dry tests have indicated Ag or Pb, or if the litmus test indi¬ 
cated an alkaline reaction, use the HNO 3 Method B. Otherwise dissolve the 
residue by the HC1 Method A. 

A. HC 1 Method of Solution.—Pour about 10 cc. HC1 (1.12) over the residue 
and warm. If solution is not complete, add 5 cc. of HC1 (1.20), and warm as 
long as any substance appears to dissolve, renewing the acid lost by evapora¬ 
tion. If the residue still remains, dilute with 5-10 cc. of water and filter by 
decantation. Pour 5 cc. aqua regia over the residue, and heat for 5-10 minutes. 
If a residue still remains, the solution must be filtered and the filtrate evap¬ 
orated, otherwise evaporate the clear solution almost to dryness; add 2-3 cc. 
more HC1 (1.20) and reevaporate to dryness over flame to expel the HN0 3 . 
Dissolve the baked residue in HC1 ( 1 . 12 ) and add H 2 0; combine with the HC1 
solution. Analyze this solution for the bases, beginning with the H 2 S Group. 

B. HNO 3 Method of Solution.—To the residue, or if the solution is alka¬ 
line, add without filtering 5-10 cc. of HN0 3 ( 1 . 20 ) and heat to boiling, and 




SYSTEMATIC ANALYSIS OF A SUBSTANCE 


223 


aporate just to dryness in a casserole by keeping the dish in motion over a 
;e flame. Dehydrate the residue, loosen from the dish, and to the powder 
d 5-10 cc. HN0 3 (1.20); warm on hot plate or steam bath 5-10 minutes; 
lute with 10-15 cc. of water; heat to boiling; filter and wash residue, adding 
e washings to the filtrate. 

C. Aqua Regia Treatment of Substances Insoluble in HC1 or HN0 3 .— 

> the residue remaining undissolved by HNO 3 add 5-10 cc. HC1 (1.20) 
id heat, adding more acid to replace evaporation. If residue still remains, 
Id to the mixture one-third of its volume of HNOa ( 1 . 20 ), heat gently as 
ng as an action continues, replacing the evaporated acids by more aqua regia, 
o the solution or the mixture, if a residue still remains, add the filtrate from 
ie HC1 Group above mentioned, evaporate nearly to dryness, and expel the 
iNOs by the method described in the “ HC1 Method of Solution," by repeated 
'aporation with HC1. 

X RESIDUE I NSOLUBLE IN ACIDS. ___ 

There are but few substances that do not go into solution under the treat¬ 
ment above prescribed. The following are the principal insoluble products 
j lat are apt to be left in this residue: 

(а) C, S (liberated by HN0 3 from sulphides). 

( б ) AgCl, (AgBr, Agl), PbS0 4 , PbCl 2 . 

(c) BaS0 4 , SrS0 4 , CaS0 4 , Si0 2 , Cr 2 0 3 , and silicates. 

(d) A1 2 0 3 , Fe 2 0 3 , Sn0 2 , Sb 2 0 3 . 

(e) CaF 2 , cyanides, ferrocyanides of the heavy metals. 

: Substances under (a), ( 6 ), and (e) have been indicated by the dry tests. 

(a) If sulphur or carbon is present, remove by ignition in a crucible. 

Residue ( 6 ), (c), (d), (e). —The halogen salts of S and C volatilize as 

ilver have been indicated in the dry tests Ag(Cl, oxides. _ 

tc., reduced to Ag by charcoal test) and the halides 

idicated by the H 2 S0 4 test. . 

The chloride and bromide are soluble in an excess of NH 4 OH, the iodide m 
, strong solution of KI. All are soluble in KCN. 

Two general procedures are used for getting refractory substances into 
olution, hydrofluoric acid treatment a nd the fusion method. _ 

A. Hydrofluoric Acid Method for Refractory Material Insoluble in 
Vqua Regia.— Transfer the residue from the acid solutions to a platinum cruci- 
)le. Add 2 cc. H 2 S0 4 (1.84), heat with moving flame until white fumes are 

















224 


QUALITATIVE ANALYSIS 


given off, then cool, add carefully, using loop of a platinum wire, 5-6 drop: 
of HF (40 per cent). Warm over a steam bath. (Bubbles are due to SiF 4 . 
Add 5 cc. more of HF (40 per cent), and cover crucible with Pt cover ant 
digest on steam or water bath 10-15 minutes unless the residue dissolve: 
more quickly. Remove the cover and evaporate, using moving flame unti 
white sulphuric acid fumes evolve. Cool and pour the contents of th< 
crucible into 10 cc. of water, and add to this the rinsing. Boil the mixture 
cool, and filter. Wash the residue first with H 2 SO 4 and then with water 
Reject the washings. 


Residue.—PbS0 4 , BaS0 4 , SrS0 4 , 
CaS0 4 , Bi 2 (S0 4 ) 3 , Cr 2 (S0 4 ) 3 , Sb 2 0 3 , 
Sn0 2 , A1 2 0 3 , Fe0,Cr 2 0 3 , and insolu¬ 
ble silicates. 

Transfer to casserole and add 15-20 

Filtrate.—Add HC1 drop by drop a; 
long as a precipitate forms. 

Precipitate.— 

AgCl, white, sol¬ 
uble in NH 4 OH. 

Test for all metah 
except Pb, Ba, Sr 
and Ag. 

cc. 01 a saiuiaieu solution 01 -LNa 2 '-'W 3 , 

boil gently 5-10 minutes, filter, and wash thoroughly. 

Residue.—Carbonates and sulphates 
Sr, Bi, Pb, Ba, and native oxides and si 
Heat with 5 cc. HC1 (1.12) and 10 cc. 1 

; of Ca, Filtrate.—Contains W. 

licates. 

d 2 0. Filter and wash. 

Residue.—Sulphates of Cr, Ba, Mo, 
and oxides of Sb, Sn, Al, Cr, etc., and 
the silicates. Fuse the residue with 

Solution.—Dilute to 40 cc. and tesl 
for Pb, Bi, Sb, Ca, Sr, Ba, which maj 
be here as chlorides. 

JNa 2 ^w 3 +lvJ\U 3 lu : l, according to 

directions given in first method. Dissolve by adding HC1 (1.12) until strong^ 
acid; evaporate to dryness, and heat over flame, cool, and add 4 cc. HC1 (1.12 
and 20 cc. H 2 0; boil and filter. 

Residue.—Si0 2 , BaS0 4 , A1 2 0 3 , Sn0 2 . 
Si0 2 and BaS0 4 by HF+H 2 S0 4 proc 
verize any remaining residue, and fuse i 
or silver crucible with solid KOH foi 
water; neutralize with HC1, extract an^ 
solution, which, of course, will contai: 

Remove Filtrate.—Test for al 

ess. Pul- elements except the alkalies 

n a nickel 

• 10-20 minutes, cool and extract with 
r residue with 5 cc. HC1(1.12). Analyze 
n Ag or Ni from the crucible. 


B. The Fusion Method of Refractory Material Insoluble in Aqua Regia.— 

Two kinds of fluxes are used: ( 1 ) Alkaline Flux , Na 2 C 0 3 (together with 
either an oxidizing agent, KN0 3 , or a reducing agent, KCN). ( 2 ) Acid Flux , 
KHSO 4 . 


















SYSTEMATIC ANALYSIS OF A SUBSTANCE 


225 


The fusion is best carried on in a platinum dish, provided no substance 
eleterious to platinum is present; otherwise in a quartz crucible. (In the 
itter case Si, Ca, and A1 may be introduced from the crucible; hence tests 
)r these are not reliable.) 

Method .—Add to the pulverized substance five times its bulk of Na 2 C0 3 (or 
mixture of 4 parts of Na 2 C0 3 + l part of KNO). Heat to high temperature 
ver a powerful flame until the mass has reached a state of quiet fusion. Cool 
nd place the crucible on its side in a small beaker, half cover with water and 
oil, adding more water if necessary. Wash the residue with boiling water 
ntil free of alkalies. (If sulphates are not present, treat the disintegrated 
ubstance directly with dilute HC1, and test for silica as stated under filtrate.) 
"ilter. 


Residue.—BaC0 3 , SrC0 3 , CaC0 3 , 
nd (a), (e). See III, page 223. 

Dissolve in a small amount of HC1 
1.12) and heat to about 100°. Add 
nore water and HC1, and filter. 

Filtrate.—Na 2 S0 4 , Na 2 Si0 3 , etc. 
Test for S0 4 by BaCl 2 test. 

For silicates, evaporate to dryness 
with HC1. See subject in Acid 
Analysis. Test for Al, Zn, Cr, As, 
and P0 4 . 




Residue ( d ), (e).—Fuse the residue 
ivith KHS0 4 at a moderate temper¬ 
ature. (High temperature will form 

Filtrate.—Ba,Sr, Ca,Cl 2 ,etc. Add to 
solution to be tested for H 2 S, (NH 4 ) 2 S 
and (NH 4 ) 2 C0 3 Groups. 

nsoluble basic sulphate.) Cool after 

10-15 minutes and dissolve in water. 

Residue.—Sn0 2 . This oxide may be 
iissolved by fusing with S and Na 2 C0 3 . 
Dissolve the Na 2 SnS 3 in water and filter. 

Filtrate—Al +++ , Cr +++ , Fe +++ 
SO 4 "' - . Test along with above 
solutions. 



_ 


If Sb is present, 
SnS 2 , will form. 


a yellow ppt., 


yTo disintegrate the Members (e).—Add 
■one. H 2 S0 4 in a platinum crucible and 
leat. HF and HCN will escape as gases. 

hang drop (water in Pt loop) held in the 
umes will absorb silicon tetrafluoride, and become cloudy. See page 188. 



















226 


QUALITATIVE ANALYSIS 


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SYSTEMATIC ANALYSIS OF A SUBSTANCE 


227 





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228 


QUALITATIVE ANALYSIS 




Aqua Regia Method 


Dissolve the alloy in a mixture of HC1 and HNO 3 (3 : 1 ) warming gently, 
dilute with water and again heat. Cool and filter. 


Precipitate.—PbCl 2 
Test for lead by usual 
procedure. 


Filtrate.—If lead has been shown to be present 
remove as a sulphate by taking to fumes with additior 
of H 2 SO 4 , cooling, diluting and filtering. 


Precipitate.—PbS0 4 Filtrate.—This may contain members of the H 2 £ 
reject. group, A and B, and members of following groups 

* The elements are separated according to the pro¬ 

cedures outlined in the tables of separations of the metals in Part II. 


Individual Tests 

Frequently it is desired to ascertain the presence of a constituent in ar 
alloy without attempting to separate the other elements present. Rapid 
tests may be made for many of the metals by more direct methods thar 
those outlined in the tables of separations. These tests may be found in the 
descriptive portions of Part II under “ Detection ” for the more common 
metals and in Part VI for the less common elements. 


Among the more familiar alloys the following are of interest. The princi¬ 
pal elements are given in heavy type under A. The less commonly occurring 
elements are given in lighter type under B. 


Name of Alloy 

Bearing metals 

Brass 

Bronze 

Britannia metal 
German silver 
Solder 
Type metal 


Composition 


a 

Copper, lead, tin 
Copper, zinc 
Copper, tin 

Antimony, tin 
Copper, nickel, zinc 
Lead, tin 

Antimony, lead, tin 


arsenic, antimony, zinc, 
arsenic, lead, tin. 
arsenic, antimony, lead, 
phosphorus, zinc, 
arsenic, copper, lead, 
arsenic, lead. 

arsenic, antimony, copper, 
arsenic, copper, cobalt, nic¬ 
kel, zinc. 


Special alloys.—Alloys containing the less common elements. 












SYSTEMATIC ANALYSIS OF A SUBSTANCE 


229 


ANALYSIS OF THE METALS 

As a general rule the number of the bases to be looked for is not large, 
and all the groups are not represented. Time is frequently saved by making 
a preliminary test for the groups present on a small portion of the sample, 
so that unnecessary addition of group reagents may be avoided in the proced¬ 
ures for complete separation of the common elements. The general scheme 
of analysis is now followed in the usual order, avoiding the groups found to be 
absent by the preliminary examination. 

• The material is dissolved according to the procedures outlined 
on pages 223 to 228. 

SEPARATION OF THE GROUPS 

To the Solution add HC1. 

Precipitate: AgCl, HgCl, PbCl 2 . 

Filtrate: Pass in H 2 S. 

Precipitate: Cd S, CuS, Bi 2 Sa, HgS, PbS, As 2 S.3, Sb 2 S3, SnS. 

Filtrate: Boil, add NH4OH and (NH^S. 

Precipitate: Al(OH) 3 , Cr(OH) 3 , FeS, CoS, MnS, NiS, ZnS . 

Filtrate: Boil, add (NH 4 ) 2 C 03 . 

Precipitate: BaCOs, CaCOs, SrCQ3. 

Filtrate contains Na, K, Mg. 

The precipitates, collected on filter papers, are thoroughly 
washed with distilled water and then dissolved and analyzed 
! according to the procedures outlined in Part II. The following 
table, pages 230 and 231, give a summary of the procedures. 




















230 


QUALITATIVE ANALYSIS 


4- 


B 


a c 

. « Pb 


£ I Bi 


§■ -f Cu' 


O -T3 Cu" 
B ! Cd 


c jz A1 

O bC *** 


O 5 £ r 

8 S _ Cr vl 

B £ 

_ 3 Fe" 

*•3 £ Fe'" 


u 

B 


Co 

Ni 


J= Mn" 
^ Mn v " 


TABLE FOR REVIEW OF THE SEPARA 


Pb 

i s 

PbCl 2 (w) 



- S- 

ii 

Hg' 

5. C/3 O 

HgCl(w) 


Ag 

1 -0 

cu 

AgCl(w) 

3* 


As'" 

As v 

Sb v 

Sb'" 

Sn ,r 

Sn" 

Au'" 


•3 PbClj Tests (a) +H 2 S0« = PbS0 4 white. (b)+H 2 S = PbS 


HgCl 


AgCl 


Add NH4OH 


Residue— NH : HgCl+Hg black. 
Solution—(NH 3 ) : (AgCl) 2 } acidify w 


| o Pt- 

friH Mo" 

2 2 

«S ^ 

U JZ 

- - Hg" 


As.S 3 (y) 
AsoSj (y) 
SbjS, (o) 
Sb 2 S 3 (oj 
SnSj (y) 
SnS (hr) 


•o 

a 

c * 

o .S 


■f 


s 6 
£ 


2 Au 2 S 3 (br) 
|PtS, (bk) 
| MoS 3 (br) 
£ 


.5 


HgS (bk) 
PbS (bk) 
Bi 2 S 3 (br) 
Cu 2 S (bk) 
CuS (bk) 
CdS (y) 


(NH,) < As 2 S 4 

(NH,) 3 AsS, 

(NH 4 ) 3 SbS« 


3 (NH 4 ) 2 SaS 3 

c 2 ...... 

Solution. 

Solution. 

(NH,) 2 MoS 4 


2 cj 

3 .t i 
— a 

T5 *c 
T3 OJ 

■0 £ 
< ^ 


As 2 S 3 
As.. S 5 
Sb 2 Sj 


SnSj 


Au 2 S 3 

PtS 2 

MoS 3 


.S A 

.2 
> u 

9 UJ 


H 3 AsO 

SbClj 

SnCI, 


AuCl a 

PtCU 

MoCU 


a. 

c J* 
>• 2 
— o 
•5 ** 

* 1 . a> 


HgS 

PbS 


Cu 2 S 

CuS 

CdS 


HgS Dissolve in nitrohyd 


£0 

c* 


■B 

2 2 

tc 3 




Pb(N0 3 ) 2 

Bi(N0 3 ) 3 

Cu(NOj)j 


Cd(NOj)j 


c'-' 

Sb 




-N 3 
< c 


± PbSO ( 
^BiiNO 
c Cu(NO 


Cd( NO 


a <« 

O 3 

_3 -e 

o S 
C/3 cj 


a . 
2 °> 
J: s 


no 


2 Al(OH) 3 (w) 
,|cr(OH) 3 (g) 

o • 

£ Fe(OH ) 3 (r) 


j= 

Bb 

"O 

<B 


o NaA10 2 

1 C/3 


Add NH4CI or rend 


.5 Cr(OH), 

o 

K Fe(OH ) 3 


Fuse on platin 
KN0 3 and Na 2 C< 
Extract with \ 


0 "2 
o 3 
— o 


< ' 


— -a 

o >. 

-O js 


•O £ 


. CoS 


12 c 


W-S 
B = 


OJ — — 


« £ 


“ o 
£ 
£ 
ej 


a 



Abbreviations: (w) = white; (y)=yel!ow; (o)-orange; (br) = brown; (bk)i 








































































SYSTEMATIC ANALYSIS OF A SUBSTANCE 


231 


(S METALS. ANALYSIS OF THE SOLUTION. 
IjCrO« = PbCrO. yellow. ( d) +KI = Pbl 2 yellow. 


I white. 


sHi gas 


bH 3 gas + Sb 


n S — 

r U 


;w 

$ c 
tc C 


^ o c-c 

s.2 ”2 rt 

^ - ® 

•C c Cl 

^ C (« 


H 3 As0 3 ] Remove AgNO 0 with CaClji and add H 2 S(AsiS 3 Lemon yellow. 
Giitzeit Test—AsH 3 colors HgCl 2 paper a deep maroon. 

, See method on page 40. 

SbAg 3 j Dissolve in hot HC1, dilute, filter and add HjS^SbjS* Orange. 


Sb 
Au 
Q % l Pt 


SnClj jTest with HgCl : . { HgCI, White; or Hg Gray. 

2 ©2 i SbCU 1 So i SbCU reject or test in Marsh apparatus. 
>-Oa I I »oO 

C--Z ( AuClj ■ - 

So! 


0 = 2 l PtCh 

c « 


f “O , . , Dissolve in nllrohydrochlorlc I A u ri, NH.C1 Evi 

= 2cO I Au acid, evaporate lo dryness wllb {. v if 

tv. excess of NH,C1 sod digest '/ignite to Au , Yellow 

§ l Pt I w m, alcohol. \ (NH 4 ) 2 PtCU Ignite I 


Evaporate and 


;luc to green-brown i Evaporate to dryness with excess of HN0 3 . 
or black solution, I excess of HC1. Test this sol. with Na 2 PHO« j 


\ (NH 4 ) 2 PtCl« Ignite to Pt 8 , Gray. 
Dissolve res. in NHL,OH and add to an 
Test this sol. with Na 2 PHO \ Ammonium phosphomolybdate, Yellow. 


\cst with (a) SnCl 2 = White HgCI or Gray to Black Hg 
ripation of Pbl 2 or PbCr0 4 Sec Pb above. 

}i(OH)j Add hot K 2 Sn0 2 pouring over ppt on filter.Bi Black. 

Deep blue solution evidence of copper. 


(6) Au wire = Hg on wire. 


:u(0H) 2 .2NH<0H.2NH 4 N0 3 

3d(OH)j2NH,OH.2NH,NOj 


For traces add HC 2 H,0 2 and test with K 4 Fe(CN)« { CihFe(CN), Red-brown. 


Add KCN till blue color disappears, then H 2 S{ CdS 


Lemon-yellow. 


1 and precipitate with (NH,) 2 C0 3 { Al(OH) 3 White, gelatinous. 

. . | K;CrO, and } Acidify with HC 2 H 3 0 2 and add Pb(C 2 H 3 0 2 ) 2 (PbCr0 4 Lemon-yellow. 

,0 ’ 1 Na 2 Cr0 4 | Dissolve in HC1 and add KCNS { Fe(CNS) 3 Blood red. Test original solution (acid) 
tes. Fe(OH)j J with KCNS for Fe'" and with K 3 Fe(CN) 6 for Fe" [ Fe 3 (Fe(CN) 6 ]i Blue 


Cb 


( a. Test with borax bead. Blue bead. c. Or evaporate + H 2 S0 4 and add nitroso-0-naphthd. 
b. Add NaHC0 3 and H.0 2| Green solution. Co—Red precipitate. Test with borax bead. 

a Test with borax bead. Brown bead. c. Or make sol. ammoniacal and add 1% 

b. He at with Br ! Ni(0 H) 3 \ add KI - • — al ™t‘ o1 ^ nitrosobetanaphthol - 

and NaOH \ ' 3 


1 / Free I in CS^ 
i(°H)i j B 0 n w ith Pb0 2 and HN0 3 ' ; HMn0 4 , Purple. 

2 Zn0 2 { Add H 2 S} ZnS White. Ppt. is insoluble in dilute acetic acid. 


ilHOUUIlb Wt. llHivouuvvuuk 

j(CH 3 ) 2 C 2 N 2 0 2 H) 2 Ni Red. 


Cr0 4 

(C 2 H 3 0 2 ) 2 

(C2Hj02)2 

Dissolve 

*6 

■cSq 

tjo'; 

in HC1 £ 

SrC0 3 

CaC0 3 

ind add H.SO^BaSO 
e „ 

|§ Sr(C 2 H 3 0 2 ) 2 

O -J 

•|w Ca(C,H 3 0 2 ) 2 

4 White. 

o m 1. Add CaS0 4 set aside 10 minutes \ SrSO« White, 
S o Moisten SrS0 4 with HC1 and apply flame test. 
® •£ 2. Add K 2 S0 4 , boil, set aside ten minutes. 

> a Filter and add f CaCj( , 4> White( nlubte in HCL 



-Apply flame test using cobalt glass. Violet, 
fa—After removal of Mg apply flame test, yellow. . 

[H 4 -To the original solution add KOH in strong excess warm (note odor) and test with moist htmuf 
paper; pass gas into Nessler’s reagent K 2 HgL sol. { NHg 2 I, Brown, 

I; (g)*grcen; (pk)-pink. Ppt. = precipitate. Res. =residue. Sol. =6olutio» 














































232 


QUALITATIVE ANALYSIS 


ANALYSIS OF THE ACIDS 

During the systematic examination for the cations, the presence 
or absence of certain acids have been ascertained. The carbon¬ 
ates, nitrites, sulphides, sulphites, etc., are volatilized by H2SO4, 
also, when H2S is passed into the solution for the analysis of that 
group, a yellow-colored solution, changing to a green, indicates 
a chromate. Then, again, the presence of phosphates was ascer¬ 
tained before completing the analysis of (NH 4 ) 2 S Group. Fur¬ 
thermore, the presence of certain metals in a solution soluble in 
water or dilute acids will indicate the absence of certain acids. 
For example, barium and the sulphate radical cannot exist in a 
solution, nor can a halide and silver be present in a salt that readily 
dissolves in water or a dilute acid. A number of acids have been 
identified by the sulphuric acid test for acids, so that our problem 
is not as complex as one might first be led to believe. Moreover, 
the number of acids to be looked for is comparatively few; this 
is especially true of natural products -such as soils, rocks, 
minerals and the like. 


General Rules for Solubilities 


Salts Soluble in Water 
Salts of Na, K, Li, NH 4 
All Nitrates and Nitrites 
All Chlorates 
All Chlorides 
All Bromides 
All Iodides 

All Sulphates 
All Acetates 

Insol. in Water, Sol. in Acids 
All Carbonates 
All Phosphates 
All Borates 
All Oxalates 
All Tartrates 

All Arsenates and Arsenites 


Exceptions 

Some basic nitrates insoluble 

Chlorides of Ag,Hg, Pb, Cu~, insoluble 
Bromides of Ag, Hg,Pb, Cu~, insoluble 
Iodides of Ag, Hg, Hg—,Pb, Cu“, 
insoluble 

Sulphates of Ba, Ca, Sr, Pb, insoluble 
Basic acetates of some metals, insol uble 

Exceptions 

The alkali salts are soluble 
The alkali salts are soluble 


The alkali salts are soluble 
The alkali salts are soluble 
The alkali salts are soluble 
The alkali salts are soluble 














SYSTEMATIC ANALYSIS OF A SUBSTANCE 


233 


Preparation of the Solution for Acid Analysis 


i Since the preparation of this solution depends largely upon the basic con- 
gtuents present, this portion of the analytical work is taken up after the 
tmpletion of the analysis of the cations. The chemist is now in a position 
t intelligently prepare the solution and to interpret reactions that will follow 
i the acid tests. 

A. Substance Soluble in Water or Dilute Acids. Heavy Metals Absent.— 
<!u, Hg, Bi, Cu, Cd, Sb, As, Sn, Fe, Al, Cr, Zn, Mn, Co, Ni, etc., sp.gr. above 
l\ Dissolve in water or dilute acid and use directly for acid analysis. 

B. Substance Soluble in Water. Heavy Metals Present.—Add to the 
ilution containing the substance 10-15 cc. of a saturated solution of Na 2 C0 3 
j d boil for 15-20 minutes, replacing water if necessary. Add about 10 cc. 
i water, and filter. 


Precipitate the heavy metals 

1 carbonates. Reject. 

t. 

Filtrate.—Filtrate containing the acids as 
ionized sodium salts. Neutralize with acetic 
acid and use for acid analysis. 


Note .—If arsenic or antimony are present among the heavy metals, acidify 
e filtrate of the insoluble carbonates with acetic acid and pass in H 2 S as long 
precipitation takes place. 

Precipitate.—Sulphides of As and 
). 

Filtrate.—Expel the H 2 S by boiling 
and use for the acid analysis. 

C. Substance Insoluble in Water.—Boil a gram of the substance with 

1 cc. of a saturated solution of Na 2 C0 3 . (Add to the substance 3-4 times 

5 bulk of the soda and a little water sufficient to dissolve the Na 2 C0 3 .) Boil 

1 minutes and filter; wash with small quantities of water. 


Residue.—Carbonates of the heavy 
letals. (Fusion with Na 2 CO 3 may be 
(icessary in some cases.) 


Filtrate.—Sodium salts of the acids. 
Acidify with acetic acid. (Excess of 
carbonate is destroyed.) Now add 
NH 4 OH in slight excess, and boil until 

! :cess is expelled. Use this solution for acid analysis. 

Notes .—If only heavy metals are present which can be precipitated by H 2 S, 
liey may be removed by suspending the solid in water and passing in H 2 S for 
pout 20 minutes. Filter and boil the filtrate to expel H 2 S, and use for analysis. 
If the solution is colored by a permanganate, it can be decolorized by boiling 
ith a few crystals of oxalic acid; filter if necessary. 

Acids used to bring the substance into solution and volatile acids should 
3 tested for in the original substance. 


















234 


QUALITATIVE ANALYSIS 


Preliminary Tests for Groups 

Silver Nitrate Group 

Acidify a portion of the solution for the acid analysis with dilute HN0 3 , an* 
add AgN0 3 solution, drop by drop, as long as a precipitate forms. Filter. 


Precipitate. —Silver the salts of the group. 


Color 

White 

Light yellow 
Orange yellow 
Black 


Inference 

C1-,CN“,C10-,SCN- 

Br-,Fe(CN ) 6 -, I - 

Fe(CN ) 6 - 

S sulphides, thiosulphites 
Add NH 4 OH to the precipitate after washing 
by decantation; shake thoroughly and filter. 


Residue.—Ag salts of Br , 

Fe(CN)«-, Fe(CN)e- 

CIO", SCN~. 

See method of analysis un¬ 
der HNO 3 Group. Part III. 


Filtrate.—Cl - , 
CN - . Add dil. 
HNO 3 and boil 
to expel —CN - . 

Residue.— 

AgCl. 


Filtrate.—The Barium an* 
Soluble Groups. Pour a fev 
drops on a white porcelaii 
tile, and place a drop 0 
NH 4 OH by means of a glas 
rod carefully on the solution 
A colored ring will appear. 

Color Inference 
Yellow H 3 AsO 3 orH 3 P0 
H 3 As0 4 
H 3 Cr0 4 

H 2 S0 3 , HP0 3 , et< 


Brown 

Red 

White 


Note .—A colored halide insoluble in strong NH 4 OH is an iodide of silvei 
AgCl is white and is easily soluble in NH 4 OH. AgBr is slightly soluble. 


Barium Chloride Group 

Make a portion of the neutral solution, just acid with a few drops of HC 
A cloudiness may be due to thiosulphates or sulphides and an oxidizin 
agent. Boil the solution and filter. Add BaCl 2 and again filter. 


Precipitate.— 
White, BaS0 4 , 
BaSiF«. Con¬ 
firm. 


Filtrate.—Add CaCl 2 and of NaC 2 H 3 0 2 . Filter. 


Precipitate.- 

-White, 

CaC 2 0 4 , CaSiO 3 . Yellow, 

CaCr0 4 . Add water and 

boil. 


Precipitate.— 

Solution.— 

CaSiOe. In¬ 

Yellow, 

soluble. 

CaCr0 4 . 


Filtrate.—Make just alk; 
line with Ba(OH ) 2 solutioi 


Precipitate.—White ind 
cates any of the followin; 
AsO, As0 4 , P0 4 , B0 3 , C 4 H 4 C 
SO 3 . Add Br water. A whi 
precipitate proves S0 3 . 


Soluble Acid Group and Organic Acids 
Members indicated by the H 2 S0 4 acid test. 

















SYSTEMATIC ANALYSIS OF A SUBSTANCE 


235 


General Summary of the Adds. 


Acids. 

Detecting Reagents. 

Reactions resulting from Test. 

Acetates 

HoS0 4 (cone.) 

Odor of vinegar 

Arsenates 

(a) (NH 4 ) 2 Mo0 4 + HN0 3 

Yellow precipitate 


(b) Magnesia mixture 

White granular precipitate 


( [c ) Reduced on C + Na 2 C0 3 

Garlic odor, arsenic mirror 

Arsenites 

( a) Magnesia mixture 

No reaction 


(b) H 2 S + HCI 

Yellow precipitate 

Bromides 

(a) H 2 S0 4 (cone.) 

Red Br vapor 


(b) Chlorine water + CS 2 

Reddish color, due to Br 

Borates 

H 2 S0 4 (cone.) + alcohol 

Green flame 

Carbonates 

Dilute acids 

C0 2 evolved. Limewater test 

Chlorates 

(a) H 2 S0 4 (cone ) 

Explosive liberation of Cl +C10 4 


(b) Heated alone 

0 given off 

Chlorides 

AgNOs + HNOs 

White precipitate, sol. inNILOH 

Chromates 

(a) H 2 S0 4 (cone.) 

0 liberated (sol. yellow to green) 


(b) HC 1 

Chlorine of HC1 liberated 


(a) Alcohol -f-NaOH 

Reduced and Cr(OH ) 3 precipi¬ 


tated 

Cyanides 

H 2 SO« (cone.) 

HCN (POISON). Odor, bitter 
almonds 

Ferricyanides 

FeS0 4 + HCl 

Turnbull's blue precipitate 

Ferrocyanides 

FeCl 3 + HC1 

Prussian blue precipitate 

Fluorides 

H 2 S0 4 (cone.) 

HFgas liberates silicic acid from 
glass rod with drop of H 2 0 

Hypochlorites 

Dilute acids 

Cl liberated, yellow gas 

Iodides 

(a) H 2 SG 4 (cone.) 

Violet vapor of iodine 


(b) Chlorine water+CS 2 

Violet color to CS 2 

Nitrates 

FcSO 4 +H 2 S 0 4 (cone.) 

Brown ring 

Nitrites 1 

Dilute acids 

N 2 0 3 brown evolved 

Oxalates 

H 2 S0 4 (cone.) 

C0 + C0 2 evolved 

Permanganates 

Reducing agents 

Decolorized 

Phosphates 

HNO a + (NH 4 ) 2 Mo0 4 at 40 ° 

Yellow precipitate 

Silicates 

(a) Fused with Na 2 C0 3 and 
HC 1 added 

Silicic acid precipitated 


(b) HF 

SiF 4 gas liberated 

Sulphates 

HCl+BaCl 2 

White precipitate of BaS0 4 

Sulphides 

Dil. acids 

H 2 S gas blackens Pb(C 2 Hs0 2 )t 

Sulphites 

Dilute acids 

S0 2 gas 

Sulphocyanides 

FeCls 

Deep red color 

Thiosulphates 

Dilute acids 

S0 2 gas + free S 

Tartrates 

Ignited 

Char. Odor of burnt sugar 

Organic acids 

Heated 

Generally char- 


» Nitrites + KI + CSj = violet color in CSa due to free I. 

















236 


QUALITATIVE ANALYSIS 


Interpretation of Results 

The Unknown in Solution. 

A simple compound in solution offers comparatively little diffi¬ 
culty for interpretation. For example, if the analysis of the cations 
proved silver to be present, and the analysis of the anions showed 
the presence of a nitrate, a report of silver nitrate in solution 
would be correct. In case of hydrolysis, however, such as takes 
place when aluminum sulphide or ferric chloride are dissolved in 
water, the problem offers greater difficulty of interpretation. The 
chemist should have a knowledge of the nature of the substance in 
order to report intelligently on the condition of the substance in 
solution. It is absurd, however, for practical purposes in qualita¬ 
tive analysis, to enter into hair-splitting distinctions. For 
example, in case of the aluminum sulphide in solution, any of 
the following might be present, depending largely on the con¬ 
centration and temperature of the solution: aluminum hydroxide 
undissociated, aluminum sulphide undissociated, aluminum 
cations, hydroxyl anions, hydrogen cations, sulphur anions, undis¬ 
sociated hydrogen sulphide. Furthermore, we are aware that 
aluminum is an amphoteric electrolyte, so that when free inorganic 
acids are added the substance acts as a weak base, and when the 
alkaline bases are added, it acts as a weak acid. 

A mixture of compounds in solution offers an insurmountable 
difficulty for the qualitative analyst, and the problem of determin¬ 
ing how the salts and acids were combined in the dry state is left 
for the quantitative analyst to unravel. Under certain circum¬ 
stances this is impossible. As example of this has already been 
cited in case of the soluble salts, sodium carbonate and potassium 
sulphate, if the gram moles are dissolved in a solution. The 
resulting mixtures would be the same, whether sodium carbonate 
and potassium sulphate were added to, say, one liter of solution, 
or whether sodium sulphate and potassium carbonate were added, 
provided the gram moles were used in each case and other con- 


SYSTEMATIC ANALYSIS OF A SUBSTANCE 


237 


ditions were the same. Hence it is not advisable for the qualita¬ 
tive chemist to attempt a combination of the acid and basic 
radicals in cases of mixed compounds in solution, but simply to 
report the metals and non-metals separately. 

i The Unknown as a Solid. 

Simple Compound.—The chemist, in dealing with solids, has 
i the advantage of a preliminary physical examination and chemical 
tests of the dry substance to aid him in his interpretation of the 
compound. In the case of a single compound the problem appears 
simple, though in reality it may involve a more careful and skillful 
interpretation than one at first would be led to believe. For exam¬ 
ple, if the chemical analysis of the material in solution would prove 
! that it contained copper and the acid radical of carbonic acid, 
it does not prove that the substance is copper carbonate, for the 
original material may contain metallic copper, copper oxide in the 
forms CU 2 O and CuO, copper hydroxide Cu(OH) 2 , and copper car- 
| bonate CuC0 3 . A physical examination of the solid, however, 

| w iH come to the rescue and enable the chemist to determine 
whether the substance is the homogeneous carbonate or a hetero¬ 
geneous substance containing the compounds mentioned, all of 
which can be recognized in the substance, provided it is not in fine 
powdered form. 

A complex mixture of compounds in solid form offers a more 
1 difficult problem to solve. The physical examination may throw 
I considerable light upon the composition of the heterogeneous sub- 
■ stance, and if it is possible to separately analyze the characteristic 
crystals of which it is composed, the difficulty of the interpretation 
; is practically obviated. However, this is not always possible, and 
! recourse must be had to certain facts obtained during the chemical 
analysis of the substance. The solubility of the material and the 
reactions during the successive treatment of the material with dif- 
ferent solvents frequently throw light upon its composition. The 
problem, however, may be twofold. First, the compounds in water 






23S 


QUALITATIVE ANALYSIS 


may form a homogeneous solution when united, or again an inter¬ 
action may take place between the two substances, resulting in less 
soluble compounds being formed. Each of the conditions will be 
taken up briefly. 

Soluble Compounds forming a Homogeneous Solution.—Sup¬ 
pose the mixture is a fine white powder which contains cadmium, 
zinc, and the hydrochloric and carbonic acid radicals. On treat¬ 
ment of the mixture with water, it is found that only a part of the 
powder dissolves, the remainder going into solution upon the addi¬ 
tion of an acid. Since we are aware that nearly all normal car¬ 
bonates are insoluble in water, an analysis of the acid solution will 
determine the metal that is in combination with the carbonate, as 
both zinc and cadmium carbonates are insoluble in water. And 
again, the analysis of the water solution will determine the metal 
in combination with the chloride, since both the metals form 
soluble chlorides. That is to say, if zinc is found in the acid solu¬ 
tion, it evidently exists in the original powder as zinc carbonate, 
and if cadmium is found in the water solution, it exists in the 
powder as a chloride, or vice versa. The oxides and hydroxides 
of these metals will likewise be found in the acid solution, and 
since these are both apt to be white, it is difficult to determine 
whether or not they are present along with the insoluble car¬ 
bonates. 

Soluble Compounds Interacting in Solution.—If an interaction 
takes place when two substances soluble in water are mixed, our 
problem becomes more complex. Take, for example, a mixture of 
potassium carbonate and calcium chloride. Both are soluble in 
water, but when their solutions are mixed, or when water is added 
to their combined solids, a precipitation of calcium carbonate takes 
place. And again, in a mixture of the soluble sodium sulphate 
and the soluble barium chloride, an immediate precipitation of 
barium sulphate takes place when water is added. In such cases 
it is impossible to determine whether barium existed as a sulphate 
in the original substance or whether calcium existed as a carbonate, 


SYSTEMATIC ANALYSIS OF A SUBSTACE 


239 


nless it is possible to separately dissolve a portion of the sodium, 
Dtassium, calcium, and barium salts and analyze them. It is 
>metimes possible to do this, when the mixture is not in a pow- 

jred form, by a primary separation of a few of the characteristic 
ystals. 



240 


QUALITATIVE ANALYSIS 




> 

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241 


The numerals indicate milligrams of the substance that will dissolve in ioo c.c. of water at stated temperature. Reference to Van Nostrand s Chemi¬ 
cal Annual, edited by Olsen. 





























242 


QUALITATIVE ANALYSIS 


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243 



* A precipitate forms on long standing. 
































244 


QUALITATIVE ANALYSIS 


Soluble Subgroup B. 



Arsenic, As'", As.. 

Antimony, 

Sb’“, Sb—. 


(ous) K 3 As0 3 . 

(ic) KH 2 AsO t . 

(ous) SbClj. 

(ic) KSbO # . 

Hydrogen 

sulphide, 

H 2 S. 

Arsenic trisul¬ 
phide, As 2 S 3 , 
yellow ppt. Sol. 
in alkalies, 
(NH 4 )*S X , 
(NH 4 ) 2 S. Insol. 
in cone. HC1. 

Arsenic trisul¬ 
phide+S. 

As 2 S 3 + S 2 , yel¬ 
low. The ppt. 
forms slowly by 
heat, 

Antimony trisul¬ 
phide. Sb 2 Ss, 
orange ppt. Sol. 
in alkalies, 
(NH 4 ) 2 S x , 
(NH 4 ) 2 S, hci 
( cone ). 0.17 mg. 

Antimony penta- 
sulphide, Sb 2 S 5 , 
orange ppt. Sol. 
in alkalies, 
(NH 4 ) 2 S X , 
(NH 4 ) 2 S, HCI 
(cone.). 

Ammonium 

hydroxide, 

NH 4 OH. 



Antimonious 
hydroxide, 
Sb(OH) 3 . white 
ppt. Sol. in 
excess. 

Ammonium 

metantimonate, 

NH 4 Sb0 3 . 

Very slightly 
sol. in excess. 

Copper sul¬ 
phate, 

CuS0 4 . 

Copper arsenite, 
CuHAsOa, yel¬ 
lowish green 
ppt. Sol in 
NH 4 OH,NaOH, 
HN 0 3 . 

Copper arsenate, 
Cu 3 (As0 4 ) 2 , 
greenish blue 
ppt Sol. in 
NH 4 OH and in 

hno 3 . 

Antimony oxy¬ 
chloride. white, 
SbOCl. caused 
by dilution. 

Insol alk. 

Sol. HCI, CS 2 . 

Copper antimo* 
nate, brown ppt. 

Mercuric 

chloride, 

HgClj. 

Mercuric arse- 
nite,Hgj(As 03 )i, 
white ppt. Sol. 
in acids. 


Antimony oxy¬ 
chloride, caused 
by dilution. 

Sol. in cone. 

HCI 


Silver ni¬ 
trate, AgN0 3 . 

Silver arsenite* 
Ag 3 As 0 3 , yel¬ 
low ppt. Sol. in 
HN0 3 , NH 4 OH, 

hc 2 h 3 o 2 . 

Silver arsenate, 
Ag 3 As0 4 , red¬ 
dish brown ppt. 
Sol. in HNOa 
and NH 4 OH. 

Silver chloride 
and antimony 
tri oxide, 

AgCl 4- Sb 2 0 3 , 
white ppts. 

Silver antimo- 
nate, Ag 2 Sb 6 3 , 
white ppt. Sol. 
in NH 4 OH. 

Miscellany. 

Magnesia mix¬ 
ture. No ppt. 
Arsenic sol. in 
HNOj, Cl t , 

HjO, aq. reg., 
hot alkalies. 

Marsh test 
(Zn-f HC1, etc-) I 

Magnesia mix¬ 
ture ppts. 
MgNH 4 As0 4 , 
white crys. ppt. 
Sol. in acetic 
acid. 

AsH 3 flame de¬ 
posits arsenic. 

Sol. in NaOCl. 
Sol. in (NH 4 ) 2 S. 
Residue insol. in 
HC1 (cone.). 

KOH ppts. 
Sb(OH) 3 . 
Na 2 C0 3 ppts. 
Sb(OH) 3 . 

* 

Marsh test 
(Zn + HCl). 

Sb. sol. in hot 
cone. H 2 S0 4 
and in aq. reg, 

SbH 3 in flame 
deposits anti¬ 
mony. Insol. in 
NaOCl. 


• Sec Van Nostrand’s Chemical Annual for solubility of salts. 












































REACTIONS OF THE METALS AND ACIDS 


245 


Hydrogen Sulphide Group 


Tim. Sn", Sn*"\ 

Platinum, Pf*\ 

Gold, Au"\ 

(ous) SnCl*. 

(ic) SnCl«. 

PtCt 4 . 

AuC1». 

r ■ 

tan nous sulphide, 
nS, dark brown. ‘ 
ol in alkalies, 
ifficultly sol in 
^H 4 ) 2 S X . Sol. in 
Cl (cone ). too c c 
2 0 diss. 0 002 mg. 

Stannic sulphide, 
SnS 2 , yellow ppt. 
Sol. in alkalies, 
(NH 4 ) 2 S X ,(NH 4 ) 2 S 
and alkali carbon¬ 
ates. HC1 (cone.). 
H 2 0— 0.02 mg. 

Platinic sulphide, 
PtS 2 , dark brown 
ppt. Difficultly 
sol. in alkali sul¬ 
phides. Sol. in 
aqua regia Insol 
in HC1 (cone.). 

Gold sulphide, 

Au 2 S 3 , black ppt. 

Sol. in alkali sul¬ 
phides, aqua regia. 
Insol in HC1 
(cone.). 

:annous hydroxide, 
rO(OH), Insol. 

excess. Darkens 

1 cooling. Insol. in 
2 0 Sol in dilute 
:ids, alk. 

Stannic hydroxide, 
Sn(OH) 4 . Slightly, 
sol. in excess. 

Ammonium chlo- 
roplatinate. 

(NH 4 x 2 PtCl 6 . yel¬ 
low ppt. Sol. in 
large excess. 

679 200 mg. 

Fulminating gold, 
Au 2 0 3 . 2 NH 3 , yel¬ 
low ppt., Insol. in 
excess. 

uprous chloride, 
CuCl, white ppt. 

> 1 . in acids- 
eduction by SnCl?. 




ercurous chloride. 
gCl, white ppt. 
isol. in cold 

Cl (cone.), 
eduction by SnCl 2 . 




lver chloride and 
Iver, AgCl + Ag. 
eduction by SnCl 2 . 

Silver chloride, 

AgCl. 

Silver chloride and 
platinum oxide, 

AgCl + PlO, 
brown ppt. 

Silver chloride and 
gold oxide. 

AgCl + Au 2 0 8 , 
brown ppt. 

OH ppts Sn(OH) 2 , 
aiC 0 3 ppts. 

(i(OH)j. Insol. in 
icess. 

KOH ppts. 

Sn(OH) 2 . NaCO* 
ppts. Sn(OH) 2 . 
Insol. in excess. 

KOH ppts. 

K 2 PtCI«. Na 2 COs 
gives no ppt. 

Pt sol. in aq r., 
fused alk. 

SnCl 2 solution 
ppts. “ Purple of 
Cassius,” red ppt. 

Au sol. in KCN, 
aq. reg. 

[etallic Sn depos¬ 
ed by Zn in 
tarsh test. 

Stannic salts 
reduced by H. gen¬ 
erated by Sn. 

Zn ppts. Pt, black, 
from its salts. 

Also see Flectro- 
motive Series p. 10 . 

Zn ppts. Au from 
its salts. 





































The Ammonium Sulphide Group. 

Numbers refer to mgs soluble in xoo c c. cold water. 


246 


QUALITATIVE ANALYSIS 















































REACTIONS OF THE METALS AND ACIDS 


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247 


• Presence of non-volatile organic substances, tartrates, citrates, and sugar prevents precipitation. 


















The Ammonium Sulphide Group — Continued 


248 


QUALITATIVE ANALYSIS 












































REACTIONS OF THE METALS AND ACIDS 


•so 

• no 

a 

Zinc hydroxide, 

Zn(0H) 2 , white ppt. 

Sol. in excess, forming 

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Manganese hydroxide, 
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Nickel hydroxide," 
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Br to Ni (0H) 3 . 

a. 

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txi 

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HCN ppts. greenish yel¬ 
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0 


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249 


For solubility of salts, see tables in D. Van Nostrand’s Chemical Annual, edited by Olsen. 






















The Ammonium Carbonate Group 

Solubility in milligrams per ioo c.c. of water cold; "c", and hot. 


250 


QUALITATIVE ANALYSIS 



C 

v 

c 


A/T nmKovo s\£ QaIiiLIa ATa+aI 


































251 


































The Soluble Group. 


252 


QUALITATIVE ANALYSIS 









































3U1BQ0D UiniDOQ 


REACTIONS OF THE METALS AND ACIDS 253 


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REACTIONS OF THE ACIDS. 
Inorganic Acids. 


254 


QUALITATIVE ANALYSIS 





































REACTIONS OF THE METALS AND ACIDS 


255 















































Inorganic Acids. 


256 


QUALITATIVE ANALYSIS 
















































REACTIONS OF THE METALS AND ACIDS 


257 





























Inorganic Acids. 


258 


QUALITATIVE ANALYSIS 














































REACTIONS OF THE METALS AND ACIDS 


259 






























Organic Acids. 


260 


QUALITATIVE ANALYSIS 

















































REACTIONS OF THE METALS AND ACIDS 


261 




























QUALITATIVE ANALYSIS 


Solubility Table. 


Since no salt is absolutely insoluble, the term “ insoluble ” is only relative. For solubility 
of the salts formed, see Van Nostrand's Chemical Annual, edited by Professor John C. Olsen. 


z 

r 1 

Cation. 


U 

u 

« 

►■H 

z 

u 

o 

2 

to 

o 

u 

o 

X 

u 

oo 

O 

u 

to 

o 

(n 

O 

to 

O 

U 

u 

OO 

capq 

•r 

O 

ft. 

O 

c/3 

< 

o 

C/3 

< 

o 

z 

u 

V 

Ue 

to 

Z 

u 

Ue 

■i 

u 

K- 

W 

W-. 

w 

w 

vv 

W 

w 

vv 

VV 

vv 

VV 

VV 

w 

W 

VV 

VV 

VV 

VV 

VV 

VV 

Na* 

W 

vv vv 

w 

w 

VV 

vv 

vv 

VV VV 

vv 

VV 

vv 

VV 

vv 

w 

vv 

vv 

W 

w 

Li* ' 

w 

w 

w 

w 

w 

vv 

vv 

vv 

vv 

vv 

vv 

vv 

vv 

VV 

w 

vv 

w 

vv 

W 

VV 

Ba- 

wa 

w 

w 

W wA 

vv 

w 

w 

vv 

A 

A 

i 

A 

A 

A 

A 

A 

— 

wA 

— 

Sr* 

wa 

w 

w 

w 

w.w 

w, 

vv 

vv 

A 

A 

1 

wA 

A 

A 

A 

A 

— 

W 

— 

Ca* 

wa 

w 

w 

w; w 

vv 

w 1 

w 

w 

A 

A 

wa wA 

A 

A 

A 

A 

vv 

W 

— 

Mg- 

wa 

w 

w 

w 

w 

vv 

VV wA W 

A 

A 

VV 

W 

wA 

A 

A 

A 

w 

w 

— 

AT“ 

W 

w 

vv 

vv' 

- 

vv 

vv 

vv 

— 

— 

wa 

VV 

— 

A 

A 

A 

— 

— 

— 

— 

Mn" 

A 

w 

w 

w 

a; 

w 

W wA 

A 

A 

A 

VV 

W 

A 

A 

A 

A 

I 

A 

— 

Zn- _ 

wA 

w 

w 

w 

A 

vv w 

w; a 

A 

A 

VV 

VV 

A 

A 

A 

— 

A 

wa 

— 

Cr* 

W 

vv vv 

vv 

A 

w 

vv 

wA 


— 

A 

w 

A 

A 

A 

A 

— 

— 

— 

— 

Cd- 

wA 

w 

w 

w 

A 

vv 

vv 

vv 

A 

A 

A 

vv vv 

wA 

A 

— 

— 

— 

— 

— 

Fe** 

wA 

w 

w 

vv 

wa 

vv 

w 

w 

A 

A 

A 

vv 

— 

A 

A 

A 

A 

I 

I 

— 

Fe~. 

W 

w 

w 

— 

— 

vv 

vV 

A 

— 

— 

A 

w 

w 

A 

A 

A 

A 

w 

I 

— 

Co- 

wAW 

w 

vv 

wa 

vv 

vv 

vv 

A 

A 

A 

vv 

A 

A 

A 

A 

A 

I 

I 

— 

Ni- 

wA'w 

vv 

w 

wa 

w 

vv 

w 

A 

A 

A 

w 

A 

A 

A 

A 

A 

I 

I 

— 

Sn- 

w 

w 

- 

w 


vv 

w 

A 

A 

— 

— 

vv 

A 

A 

A 

— 

— 

1 

I 

— 

Sn— 

w 

w 

— 

vv 





A 






A 

A 

A 

— 

I 

— 

Pb” 

A 

w w 

vv 

A 

w 

vv 

vv 

A 

A 

A 

I 

I 

A 

A 

A 

— 

wA 

A- 

— 

Cu- 

A 

w 

w 

I 

I ;W 

w 

vv 

A 

A 

— 

vv 

VV 

A 

A 

A 

A 

— 

I 

— 

Sb- 

W 

A 

A 

wA 

— 


— 

A 

A 

— 

— 

A 

A 

— 

A 

A 

— 

— 

— 

— 

Bi- 

W 

A 

A* 

A 

— 

A 

vv 

A 

A 

A 

A 

A 

A 

A 

A 

A 

— 

— 

— 

— 

Hg- 


I 

I 

I 

— 

w 

w 

A 

— 

A 

— 

wA 

A 

— 

A 

A 

A 

— 

— 

— 

Hg- 

wA 

w 

w 

A 

W 

w 

vv 

A 

A 

A 

— 

VV wA 

— 

A 

A 

A 

— 


— 

Ag- 

W 

I 

I 

I 

I 

vv 

w 

A 

A 

A 

A 

wA 

A 

A 

A 

A 

A 

A’ 

I 

— 

Pt— 

— 

w 

w 

I 

VV 

vv 

— 

— 

A 

— 

— 

VV 

— 

— 

— 

— 

A 

■— 

— 

— 

Au- 

— 

w 

w 

A 

VV 





1 









•• 



Abbreviations. — W = soluble in water; A = soluble ip acids; wA =.slightly soluble 
in water, readily soluble in acids; wa= difficultly soluble in water and in acids; I — insol¬ 
uble in water and acids. 

The metals are arranged in order of their electromotive series. 








































































263 


REACTIONS OF THE METALS AND ACIDS 


INTERNATIONAL ATOMIC WEIGHTS, 1918 


ELEMENT. 

SYMBOL. 

ATOMIC 

WEIGHT. 

uminum. 

A1 

27.1 

itimony. 

Sb 

120.2 

gon. 

A 

39.88 

senic. 

As 

74.96 

uium. 

Ba 

137.37 

smuth. 

Bi 

208.0 

iron. 

B 

11.0 

omine. 

Br 

79.92 

idmium. 

Cd 

112.40 

lesium. 

Cs 

132.81 

ilcium. 

Ca 

40.07 

Iirbon. 

C 

12.005 

irium. 

Ce 

140.25 

llorine. 

Cl 

35.46 

jiromium. 

Cr 

52.0 

>balt. 

Co 

58.97 

)lumbium. 

Cb 

93.1 

i)pper. 

Cu 

63.57 

ysprosium. . . . 

Dy 

162.5 

•bium. 

Er 

167.7 

iropium. 

Eu 

152.0 

uorine. 

F 

19.0 

idolinium. 

Gd 

157.3 

rllium. 

Ga 

69.9 

brmanium. 

Ge 

72.5 

Lucinum. 

G1 

9.1 

f>ld. 

Au 

197.2 

elium. 

He 

4.0 

plmium. 

Ho 

163.5 

ydrogen. 

H 

1.008 

idium. 

In 

114.8 

idine. 

I 

126.92 

idium. 

Ir 

193.1 

on. 

Fe 

55.84 

typton. 

Kr 

82.92 

inthanum. 

La 

139.00 

3ad. 

Pb 

207.20 

ithium. 

Li 

6.94 

atecium. 

Lu 

175.0 

[agnesium. 

Mg 

24.32 

[anganese. 

Mn 

54.93 

[ercury. 

Hg 

200.6 


ELEMENT. 

SYMBOL. 

ATOMIC 

WEIGHT. 

Molybdenum. . . 

Mo 

96.0 

Neodymium.... 

Nd 

144.3 

Neon. 

Ne 

20.2 

Nickel. 

Ni 

58.68 

Niton. 

Nt 

222.4 

Nitrogen. 

N 

14.01 

Osmium. 

Os 

190.9 

Oxygen. 

O 

16.00 

Palladium. 

Pd 

106.7 

Phosphorus. 

P 

31.04 

Platinum. 

Pt 

195.2 

Potassium. 

K 

39.10 

Praseodymium. . 

Pr 

140.9 

Radium. 

Ra 

226.0 

Rhodium. 

Rh 

102.9 

Rubidium. 

Rb 

85.45 

Ruthenium. 

Ru 

101.7 

Samarium. 

Sa 

150.4 

Scandium. 

Sc 

44.1 

Selenium. 

Se 

79.2 

Silicon. 

Si 

28.3 

Silver. 

Ag 

107.88 

Sodium. 

Na 

23.00 

Strontium. 

Sr 

87.63 

Sulphur. 

S 

32.06 

Tantalum. 

Ta 

181.5 

Tellurium. 

Te 

127.5 

Terbium. 

Tb 

159.2 

Thallium. 

T1 

204.0 

Thorium. 

Th 

232.4 

Thullium. 

Tm 

168.5 

Tin. 

Sn 

118.7 

Titanium. 

Ti 

48.1 

Tungsten. 

W 

184.0 

Uranium. 

U 

238.2 

Vanadium. 

V 

51.0 

Xenon.. 

Xe 

130.2 

Ytterbium. 

Yb 

173.5 

Yttrium. 

Yt 

88.7 

Zinc. .. 

Zn 

65.37 

Zirconium. 

Zr 

90.6 





























































































INORGANIC COMPOUNDS 


264 


QUALITATIVE ANALYSIS 


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I 






PART VI 


THE LESS COMMON ELEMENTS 

RARER ELEMENTS OF THE HYDROGEN SULPHIDE GROUP 

GOLD 

u, at.wt. 197.2; sp.gr. 19.33; m.p. 1063; b.p. 2630° C.; oxides, Au 2 0, Au 2 0 3 . 

Gold is a soft, malleable, ductile, yellow metal. It appears red or bluish 
iolet in fin ely divided form. It is precipitated from solution as a dark brown 
owder. Gold forms two series of compounds, aurous and auric. 

Solubility.—Gold in massive form is practically insoluble in pure nitric, 
llphuric or hydrochloric acids, but in the presence of oxidizing agents, is 
ttacked appreciably by sulphuric, and actively by hydrochloric acid. Gold 
i found in minute quantity in the nitric acid solution of its alloys, and in such 
s contain selenium, the amount may be a large part of the total alloy present. 

Gold is attacked energetically by aqua regia. Large amounts of gold are 
issolved with requirement of least attention when the proportion of hydro- 
hloric acid is several times that of the aqua regia formula, (3HC1 . 1HN0 3 ). 

Gold is dissolved by solutions of chlorine or bromine, by alkaline thio- 
ulphates; in the presence of free oxygen by iodine in potassium iodide solu- 
ion, by soluble cyanides, by fused potassium or sodium hydroxide; by fused 
otassium or sodium nitrate or sulphide. In a finely divided state, it is dis- 
olved by a solution of potassium or sodium hydroxide. 

Gold alloys quickly with molten lead. When in the form of bright, untar¬ 
nished particles it alloys readily with mercury. 

DETECTION 

Because of the limited application and tediousness of wet methods, the 
letection of a small quantity (2 parts per million or less) of gold m a mineral or 
>ase metal is most positively carried out by furnace metho s o assaying. 
Vet methods of detection of traces of gold can be applied only to solutions 
ree of colored salts and elements precipitated by the reagents employe . s 
t rule, in the treatment of an unknown substance, advantage is taken of the 
lolubility of most metals and their compounds, and insolubility of go y 
me of the mineral acids. 


293 





294 


QUALITATIVE ANALYSIS 


Detection of Gold in Alloys. —In metals or alloys which produce colorles 
solutions with dilute nitric acid, gold, in the absence of other insoluble matter 
appears as a black or brownish residue which settles readily, and from whicl 
the liquid can be Separated by careful decantation. If unassociated witl 
metals of the platinum group, this residue will become yellowish brown oi 
heating with strong nitric acid. 

In copper, nickel and such alloys, which leave a residue of sulphur, carboi 
or silicious matter on treatment with dilute nitric acid, the solution is filterec 
through double ashless filters and the filter and residue incinerated in i 
porcelain crucible. The residue, which may require pulverizing, is digestec 
for a few minutes with aqua regia, and the dilute, filtered solution evaporatec 
to dryness by heating below 200° F. Just as soon as dry, the mass is moist 
ened with the least quantity of hydrochloric acid and the purple of Cassiu? 
test applied to its water solution in a small volume. This test is made bj 
adding a solution of stannous chloride, containing stannic chloride. Ir 
strongly acid and concentrated gold solutions a precipitate of brown metalli< 
gold is obtained. If the solution is but slightly acid and dilute, a reddish 
purple color is produced by colloidal gold and the stannic acid. The tinl 
fades on standing. Addition of ammonia produces a red coloration. 

This test applied to 1 part of gold in 600,000 of solution will impart a per¬ 
ceptible shade; to double this quantity, a mauve color. When gold is presenl 
in somewhat greater proportion a flocculent precipitate will form. 

Test for Gold in Minerals.—From minerals, in which the metal exists ir 
unalloyed, or uncombined state, gold may be extracted by iodine in potassiuir 
iodide solution, or by chlorine or bromine water. All minerals containing 
sulphides should be roasted. In natural or roasted state the sample should 
be very finely pulverized, and usually yields the gold best if first digested 
with nitric acid and washed free of soluble salts. The sample in a flask is 
covered with bromine water, the flask closed with a plug and shaken frequently 
during a period of three or four hours. The purple of Cassius test is applied 
to the extract, removed by decantation after concentration. 

If it is evident that base metals are present in the bromine water extract 
in quantity sufficient to mask the purple of Cassius test, hydrogen peroxide 
is added to the concentrated liquid, slightly alkaline with sodium or potassium 
hydroxide or carbonate. After boiling the solution until hydrogen peroxide 
is removed, precipitated hydroxides or carbonates are dissolved by hydro¬ 
chloric acid. Gold in exceedingly small quantity exhibits itself as a light- 
brown residue in a fine filter. This indication should be confirmed by a purple 
of Cassius test on the aqua regia solution of the residue; the test carried out 
in the same manner as on the residue from a solution of a metal. 

Benzidine Acetate Tests. —Maletesta and Nola make use of benzidine 


THE LESS COMMON ELEMENTS 


295 


cetate (1 gram benzidine dissolved in 10 cc. acetic acid and 50 cc. water) 
3 a reagent in the detection of gold and platinum in quite dilute solutions, 
lold gives a blue coloration which gradually changes to violet. The colora- 
ion is green in the presence of free acetic acid, changing to blue with addition 
f benzidine in excess. Platinum gives a blue flocculent precipitate, the 
Drmation of which is promoted by heating. Free mineral acids have no 
lfluence on the gold and retard the platinum reaction only in the cold. Since 
3 rric salts give a blue coloration, stable only in excess of benzidine, their 
bsence must, be assured before application of the test for the precious metals. 
?he limi t, of sensitiveness of the test is 35 parts for gold and 125 parts for 
platinum per 10,000,000. 

Phenylhydrazine Acetate Test—E. Pozzi Escot adds phenylhydrazine 
.cetate to a very dilute gold solution which contains an excess of an organic 
!cid (formic or citric). A violet coloration, permanent for several hours, is 
mparted. The depth of color is proportional to the quantity when the gold 
3 present in less amount than one part in 500,000. 


PLATINUM 

Pt, at.wt. 195.2; sp.gr. 21.48; m.p. 1755° C.; oxides PtO, Pt0 2 . 
Platinum is a gray, lustrous, soft and malleable metal. It is not altered by 
rnition in the air, but fuses in the oxy-hydrogen flame. It does not dissolve 
i any of the single acids, but a fusion with acid potassium sulphate attacks 
le metal slowly. The action of chlorine in general, and mtro-hydrochlonc 
cid (aqua regia), the main solvent, converts the metal to hydrochlorplatinic 
cid HaPtCle, which forms many double salts, or platinochlondes. If platimc 
hloride is gently heated it breaks up into platinous chloride, PtCl 2 , and 

^ Platinum alloyed with silver, may be dissolved by nitric acid to a yellow 
auid provided sufficient silver is present in the alloy. Platinum forms 
asible alloys with arsenic, antimony, phosphorus, boron, silicon, and most 
f the metals; hence these metals, and readily reducible compounds should 
l0t be heated in platinum vessels. The coefficient of expansion is the same 
,s that of glass, so that a platinum wire can readily be sealed into a glass rod. 
Since the metal may be either divalent or tetravalent, it has two senes of 

ompounds. . .... 

Platinum may be present under the following conditions. 

1. Native grains usually accompanied by the other so-called platinum 



296 


QUALITATIVE ANALYSIS 


metals, iridium, palladium, ruthenium, rhodium, and osmium, together wit 
gold and silver (alloyed with one or more of the allied metals). 

Ore concentrates containing the native grains, as above, with the bas 
metals, iron, copper, chromium, titanium, etc. The associated mineral i 
high in specific gravity in the gravels may be expected to appear with thi 
platinum nuggets, such as chromite, magnetite, garnet, zircon, rutile, sma 
diamonds, topaz, quartz, cassiterite, pyrite, epidote, and serpentine; wit 
gold in syenite; ores of lead and silver. 

2. Scrap platinum containing, oftentimes, palladium, iridium, gold, silve 
and iron. 

3. Small amounts of platinum in the presence of large amounts of iror 
silica, carbon, magnesia: platinum, residues, nickel and platinum contacts 
photography paper, jewelers’ filings and trimmings, dental and jewelers 
sweeps and asbestos, etc. 

4. Platinum alloyed with silver, gold, tungsten, nickel, copper, lead, etc. 

5. Platinum solutions and salts. 

Solubility.—The best solvent for platinum is aqua regia. The metal i 
also acted upon by fusion with the fixed alkalies—sodium or potassium hydrox 
ide and sodium peroxide or potassium or sodium nitrate; also by fusioi 
with acid potassium sulphate. The element dissolves in nitric acid whei 
alloyed with a sufficient amount of silver (distinction from gold). 

All salts of platinum are soluble in water. The less .soluble salts are th 
chloroplatinates of potassium, ammonium, rubidium and caesium. Hea 
increases the solubility, while the presence of alcohol decreases the solubility 

DETECTION 

Ammonium chloride added to a concentrated solution of platinum chloridi 
precipitates yellow (NH 4 ) 2 PtCl 6 , which is slightly soluble in water, but insol 
uble in dilute ammonium chloride solution and alcohol. 

Ferrous sulphate precipitates metallic platinum on bo ilin g from a neutra 
solution. Neutralize with Na 2 C0 3 . Free mineral acids prevent the precipi 
tation (different from gold). 

Formic acid precipitates from neutral boiling solutions all the platinum as 
a black metallic powder. 

Hydrogen sulphide precipitates black platinum disulphide, PtS 2 , with the ! 
other elements of the hydrogen sulphide group. The solution should be warm ! 
as precipitation takes place more quickly. It is difficultly soluble in ammo 
nium sulphide. It will be found in the extract with the arsenic, antimony, 
tin, gold, molybdenum, etc., and is precipitated with these elements upon 
addition of hydrochloric acid. Platinum sulphide is soluble in aqua regia. 

Oxalic acid does not precipitate platinum (difference from gold). 







THE LESS COMMON ELEMENTS 


297 


Potassium chloride precipitates yellow K 2 PtCl6, which is difficultly soluble 
a water, but insoluble in 75 per cent alcohol. 

Potassium iodide precipitates platinum iodide, but it dissolves quite 
eadily, giving a pink to a dark blood-red liquid, depending on the concen- 
ration of the solution. Nitric acid should be absent. Heat destroys this 
olor, as well as hydrogen sulphide, sodium thiosulphate and sulphite, sul- 
ihurous acid, mercuric chloride and certain other reagents. 

Sodium hydroxide with glycerine reduces hydrochlorplatinic acid on warm- 
tig to black metallic powder. 

Stannous chloride does not reduce platinum chloride to metal, but reduces 
tydrochlorplatinic acid to hydrochlorplatinous acid. 

H 2 PtCl6+SnCl 2 =H 2 PtCl 4 +SnCl 4 . 

Metallic zinc, magnesium, iron, aluminum and copper are the most im- 
>ortant metals that precipitate metallic platinum. 

H 2 PtCl6+3Zn = 3ZnCl 2 +H 2 +Pt. 




298 


QUALITATIVE ANALYSIS 


RARER ELEMENTS OF THE ALLIED PLATINUM METALS 

IRIDIUM 

Element, Iridium. Ir. at.wt. 193.1; sp.gr. 22.3; m.p. 2350° C.? oxide 

Ir0 2 , Ir 2 Oi. 

Iridium is found associated with platinum. The element is insoluble in al 
acids, including aqua regia. Chlorine is the best reagent which forms th 
chlorides of iridium and yields compounds with other chlorides as K 3 IrCle 
which is insoluble. If the element is heated in a stream of chlorine in th 
presence of potassium chloride there forms a salt, K 2 IrCl 6 , which is sparingly 
soluble and is used in the separation of iridium. 

Substances in which iridium is determined are few, namely: platinun 
scrap, jewelers’ sweeps, contact points, ores, etc. 

Solution of Iridium Alloys.—Platinum scrap and contact points, etc. 
containing iridium dissolve with difficulty in aqua regia, depending on th 
amount of iridium present. The alloy is dissolved quicker if it is rolled o 
hammered to a very thin sheet or ribbon. The alloy of platinum and iridiun 
with an iridium content up to 10 per cent dissolves in aqua regia slowly; ai 
alloy of iridium content of 15 per cent dissolves in aqua regia very slow! 
and the aqua regia will likely have to be replenished from time to time. Ai 
alloy of 25 per cent iridium is practically insoluble in aqua regia. The filing 
from the sweeps, etc., can be dissolved by aqua regia the same as the scrap. 

DETECTION 

Caustic Alkalies produce in a boiling solution a dark-blue precipitate o 
Ir(OH) 4 insoluble in all acids except HC1. 

Potassium chloride forms the double salt of K 2 IrCl6, which is black and i 
difficultly soluble in water. 

Ammonium chloride precipitates black (NH 4 ) 2 IrCl 6 , which is difficult! 
soluble in water. 

Hydrogen sulphide precipitates black Ir 2 S 3 , soluble in (NH 4 ) 2 S. 

Metallic zinc precipitates from an acid solution black metallic iridium. 

Formic acid and sulphurous acid precipitate black metallic iridium froc 
hot solutions, 








THE LESS COMMON ELEMENTS 


299 


OSMIUM 

Element, Osmium. Os, at.wt. 190.9; sp.gr. 22.4; m.p. 2700° C.? oxides 
OsO, 0s 2 0 3> 0s0 2 , 0s0 4 . 

Osmium occurs with platinum ores and alloyed with iridium. The chlo- 
ides, OsCl 2 and OsCl 4 , combine with the alkali chlorides. Osmium oxidizes 
asily and burns in the flame. Through the action of HN0 3 , aqua regia or 
mating in a stream of moist chlorine, osmic tetroxide is formed. Osmium 
5 very volatile and the fumes are poisonous. It is detected readily by the 
dor when heated, as the fumes are highly corrosive and disagreeable like 
hlorine. Chlorine passed over hot osmium mixed with KC1 gives K 2 0sCl 6 , 
diich dissolves in cold water. 

Osmium is estimated mainly in osmiridium and platinum residues. 

Solution.—After the platinum is extracted the residue or osmiridium is 
nixed with two or three times its weight of common table salt. The mixture 
s put in a porcelain or silica tube and heated to a dull red heat; moist chlorine 
Is then passed through the tube for a short time. The mass is cooled and 
lissolved with water. After several treatments the entire group of platinum 
. netals will be in solution. 

The osmium material may also be fused with KOH and KNO3 and the 
nelt dissolved in water. The osmium will be in solution as potassium 
, ornate, K 2 0s0 4 , while the iridium remains as residue. 

DETECTION 

Hydrogen sulphide precipitates brownish black osmium sulphide, OsS 4 , 
ifbut only in the presence of some strong mineral acid. It is insoluble in ammo¬ 
nium sulphide. 

Potassium hydroxide precipitates reddish-brown osmium hydroxide. 

1 Ammonium hydroxide precipitates the osmium hydroxide. 

Zinc and formic acid precipitate black metallic osmium. 

Hydrogen reduces osmium compounds to the metal. 

PALLADIUM 

Element, Palladium. Pd. at.wt. 106.7; sp.gr. 11.9; m.p. 1649° C.; oxides 

Pd 2 0, PdO, Pd0 2 . 

This metal is also found associated with platinum and iridium as well as 
ruthenium, rhodium, and osmium. It occurs in the metallic state sometimes 
with gold and silver. It resembles platinum as to lustre and color. Palladium 




300 


QUALITATIVE ANALYSIS 


sponge when heated slightly gives a rainbow effect due to the formation c 
oxides. Hydrogen passed over the sponge restores it to the original color. 

Palladium is determined in alloys, ores, jewelers’ sweeps, etc. 

It dissolves in HN0 3 and boiling H 2 SQ 4 . HC1 has little action upon il 
It is readily soluble in aqua regia, forming PdCl 2 . Palladium when alloye 
with platinum, or an alloy of platinum, iridium and palladium, dissolve 
with the other metals in aqua regia as the chloride. When palladium 
alloyed with silver the palladium and silver are dissolved in HNO3. 

Compounds of Palladium. Soluble.—Chloride, PdCl 2 2H 2 0 red brown 
nitrate, Pd (NO 3)2, brown; sulphate, PdS0 4 -2H 2 0 brown; Insoluble- 
bromide, PdBr 2 , brown; cyanide, Pd(CN) 2 , yellow; iodide, Pdl 2 , black 
Oxides, Pd 2 0, PdO, Pd0 2 , black; sulphides, Pd 2 S, gray; PdS, black. 

DETECTION 

Alkalies precipitate a dark-brown precipitate soluble in excess of th 
reagent. If boiled a brown palladous hydroxide is precipitated. The anhy 
drous oxide is black. 

Ammonia gives a flesh-red precipitate, PdCl 2 NH 3 , soluble in excess o 
ammonia. If HC1 is added to this solution the yellow compound of pallad 
ammonium chloride, Pd(NH 3 Cl) 2 , is deposited. 

Ammonium chloride precipitates palladium as (NH 4 ) 2 PdCl 4 from th 
nitrate. 

Ferrous sulphate slowly produces a black precipitate of metallic palladiun 
from the nitrate. 

Formic acid, zinc and iron literate to metallic palladium from its solutions 

Hydrogen sulphide precipitates black palladous sulphide, PdS, soluble ii 
HC1 and aqua regia, but insoluble in (NH 4 ) 2 S. 

Mercuric cyanide precipitates a yellowish-white gelatinous precipitate 
Pd(CN) 2 , insoluble in dilute acids, but dissolving in ammonia and in potassiun 
cyanide to K 2 Pd(CN) 4 . 

Potassium iodide precipitates black palladous iodide, Pdl 2 , insoluble ii 
water, alcohol, and ether, but soluble in an excess of the reagent. 

Potassium nitrite precipitates a yellow crystalline powder, K 2 Pd(N0 2 ) 4 . 







THE LESS COMMON ELEMENTS 


301 


RHODIUM 

;lement, Rhodium. Rh, at.wt. 102.9; sp.gr. 12.1; m.p. 1950° C.; oxides 
RhO, RI 12 O 3 , Rh0 2 . 

DETECTION 

Rhodium is found only in platinum ores. It is a white metal, difficultly 
osible, and insoluble in acids. Rhodium, however, dissolves in aqua regia 
/hen alloyed with platinum, to a cherry-red solution. It is also soluble in 
lolten phosphoric acid and dissolves when fused with acid potassium sulphate 
rith the formation of K 3 Rh(S0 4 )3. If the metal is treated with chlorine 
1 the presence of sodium chloride there forms a soluble salt, Na 3 RhCl 6 . 

Rhodium is estimated mainly in ores, thermo couples and salts. 

Solution of Alloys. —When rhodium is estimated in thermo couples or 
ther alloys of platinum and rhodium the wire or sample is rolled to a thin 
ibbon and dissolved in aqua regia. Both metals will go into solution, forming 
he chlorides of rhodium and platinum. The aqua regia will have to be 
ieplaced from time to time, as the alloy dissolves slowly. 

The rhodium from salts is precipitated with zinc and the black metallic 
hodium cleaned with dilute aqua regia, filtered, washed, ignited and reduced 
rith hydrogen. 

Some alloys and ores are alloyed with silver and the silver and platinum are 
[issolved in HN0 3 . Rhodium is in the residue. 

DETECTION 

Hydrogen sulphide precipitates from a hot solution and incompletely a 
>rown rhodium sulphide, Rh 2 S 3 . 

Potassium hydroxide precipitates at first a yellow hydroxide, Rh(OH) 3 
fH 2 0 soluble in an excess of the reagent. If boiled, a gelatinous, dark- 
brown hydroxide, Rh(OH) 3 , separates. A solution of Na 3 RhCl 6 does not 
how this reaction immediately, but the precipitate appears in the course of 
ime. An addition of alcohol causes a black hydroxide to be precipitated 
at once. 

Ammonium hydroxide produces a yellow precipitate of Rh(NH 3 ) 6 Cl 3 
vhich is insoluble in HC1. 

Potassium nitrite precipitates from hot solutions a bright yellow precipi¬ 
tate of double nitrite of potassium and rhodium. 

Zinc, iron and formic acid precipitate rhodium as a black metal. 

Hydrogen reduces rhodium salts. 






302 QUALITATIVE ANALYSIS 

RUTHENIUM ' 

Element, Ruthenium. Ru. at.wt. 101.7; sp.gr. 12; m.p. 2450° C.? oxide 
RuO, Ru 2 0 3 , Ru0 3 , Ru0 4 . 

This element is found only in platinum ores. It is barely soluble in aqu 
regia, and insoluble in acid potassium sulphate. It dissolves when fuse 
with KOH and KN0 3 . The solution of the fusion when dissolved in wate 
forms potassium rutheniate, K 2 Ru0 4 , from which HN0 3 precipitates th 
hydroxide, which is soluble in HC1. The treatment with chlorine and KC 
at a high temperature yields a salt of K 2 RuCl6. The salts that are most com 
mon are K 2 RuC 1 5 and K 2 RuCl6. 

Ruthenium is generally estimated in alloys and ores or residues. 

Solution of Alloys.—When ruthenium is alloyed with platinum or golc 
aqua regia dissolves these metals, forming the chlorides of platinum, go] 
and ruthenium. The ruthenium in ores is in the form of an alloy with plat 
num or osmiridium. This is fused with KN0 3 and KOH in a silver crucibk 
the osmium and the ruthenium forming salts while the iridium remains as a 
oxide. 

DETECTION 

Potassium hydroxide precipitates a black hydroxide easily soluble in HC 

Hydrogen sulphide slowly produces black Ru 2 S 3 . 

Ammonium sulphide precipitates brownish black sulphide. 

Metallic zinc precipitates metallic ruthenium, the solution first turnin 
blue. 







THE LESS COMMON ELEMENTS 


303 


MOLYBDENUM 

[o, at.wt. 96.0; sp.gr. 8.6-9.01; m.p. 2600° C.; oxides, M 2 0 3 , Mo0 2 , Mo0 3 . 

Metallic molybdenum is softer than steel, malleable and capable of being 
.rged and welded. The metal combines with the halogens to form a number 
' salts. It forms compounds with phosphorus, boron, silicon, sulphur, 
irbon, and alloys with iron and other metals. 

The determination is required in the ores—molybdenite, MoS 2 (60 per 
mt Mo;) molybdite, MoO a (straw yellow); wulfenite, PbMo0 4 (yellow, bright 
;d, olive green or colorless); Ilsemannite, Mo0 3 + Mo0 2 ; powellite, CaMo0 4 ; 
iteraite, CoMo0 4 ; belonesite, MgMo0 4 ; eosite, lead-vanado-molybdate; 
3 hromatite, lead molybdate and arsenate with tin oxide and lead chloride, 
ome iron and copper ores also contain molybdenum. 

The metal is determined in certain self-hardening steels and alloys. 

The reagents ammonium molybdate and the oxide-molybdic acid, Mo0 3 , 
re valuable for analytical purposes. 

, Solubility—In dissolving the substance the following facts should be 
ept in mind: The metal is easily soluble in aqua regia; soluble in hot con- 
sntrated sulphuric acid, soluble in dilute nitric acid, oxidized by excess to 
jlo0 3 . It is dissolved by fusion with sodium carbonate and potassium 
itrate mixture. It is insoluble in hydrochloric, hydrofluoric and dilute 
ulphuric acids. 

The oxide Mo0 3 is but slightly soluble in acids and alkalies; Mo0 2 is insolu¬ 
ble in hydrochloric and hydrofluoric acids. Mo0 3 , as ordinarily precipitated, 
i soluble in inorganic acids and in alkalies. The oxide sublimed is difficultly 
ioluble. 

Molybdates of the heavy metals are insoluble in water, the alkali molyb- 
lates are soluble. 

Ores.—Molybdenum ores are best decomposed by fusion with a mixture 
,f sodium carbonate and potassium nitrate. The cooled fusion is then 
;xtracted with hydrochloric acid. 

Steel and Iron—The drillings are dissolved in a mixture of hydrochloric 
md nitric acid (25 cc. HC1+1 cc. HNO 3 ), with gentle heating. Additional 
litric acid is added if required or potassium chlorate may be used to oxidize 
he iron. 

DETECTION 

Molybdenum appears in the hydrogen sulphide group, being precipi¬ 
tated by H 2 S in acid solution as the sulphide. It passes into solution by 
digestion with ammonium sulphide or sodium sulphide along with arsenic, 
; intimony, tin, gold and platinum. By addition of metallic zinc, antimony, 





304 


QUALITATIVE ANALYSIS 


together with tin, gold and platinum are precipitated as metals whi 
molybdenum remains in solution. Arsenic, that has not volatilized 
arsine, is expelled by evaporation. Nitric acid is now added and the soli 
tion taken to dryness. Molybdenum is extracted from the residue wit 
ammonium hydroxide. 

A dilute solution of ammonium molybdate treated with a solub 
sulphide gives a blue solution. 

Sodium thiosulphate added to a slightly acid solution of ammoniui 
molybdate produces a blue precipitate with a supernatant blue solutioj 
With more acid a brown precipitate is formed. 

Sulphur dioxide produces a bluish-green precipitate if sufficient molyt 
denum is present, or a colored solution with small amounts. The reducin 
agents, stannous chloride, or zinc in acid solution, produce a play of coloi 
when they react with molybdenum solutions, due to the formation of th 
lower oxides. The solution becomes blue, changing to green, brown an 
yellow. 

Molybdenum present as molybdate is precipitated by disodium pho. 
phate as yellow ammonium phosphomolybdate from a nitric acid solutioi 
The precipitate is soluble in ammonium hydroxide. 

A pinch of powdered mineral on a porcelain lid, moistened with a fe 
drops of strong sulphuric add, stirred and heated to fumes, then coolet 
will produce a blue color when breathed upon. The color disappears o 
heating, but reappears on cooling. Water destroys the color. 

Molybdenite is very similar to graphite in appearance. It is distil 
guished from it by the fact that nitric acid reacts with molybdenite, MoS 
leaving a white residue, but has no action upon graphite. The blowpij 
gives SO 2 with molybdenite and CO 2 with graphite, 


SELENIUM AND TELLURIUM 

Se 8 at.wt. 79.2; sp.gr. 

Se0 2 ; acids, H 2 Se0 3 , H 2 Se0 4 . 


(=r,“r* :m, w **>•'■>«" 


Te, at.wt. 127.5; sp.gr. 6.27; m.p. 452°; b.p. 1390° C.; oxides TeO, TeO 
Te0 3 ; acids, H 2 Te0 3 , H 2 Te0 4 . 

Selenium and tellurium closely resemble sulphur in chemical propertie 
They have crystalline and amorphous forms. The elements occur in natui 
frequently associated with sulphur. Selenium is frequently present, in iro 




THE LESS COMMON ELEMENTS 


305 


writes, hence is found in the flue dust of lead chambers of the sulphuric acid 
ant, and as an impurity in sulphuric acid, prepared from pyrites containing 
lenium. 

Selenium occurs in copper and iron pyrites; meteoric iron. In the rare 
inerals clausthalite, PbSe; lehrbachite, PbSe-HgSe; onofrith, HgSe • 4HgS; 
icairite, CuSe-Ag 2 Se; crookesite, (CuTlAg)Se. 

Tellurium.—Occurs in tellurides and arsenical iron pyrites. Frequently 
ssociated with gold, silver, lead, bismuth and iron. In the minerals—altaite, 
bTe; calaverite, AuTe 2 ; coloradolite, HgTe; nagyagite, (AuPb) 2 (TeSSb) 3 ; 
itzite, Ag 3 AuTe 2 ; sylvanite, AuAgTe 4 ; telluride, Te0 2 (tellurium ochre); 
tradymite, Bi 2 Te 3 . 

Solubility. Selenium.—Amorphous selenium is soluble in carbon disul- 
lide; the crystalline hexagonal form is insoluble in this reagent. The 
etal is soluble in hydrochloric acid in the presence of nitric acid. It is 
tluble in cold concentrated sulphuric acid, forming a green-colored liquid, 
hich diluted with water deposits selenium. The dioxide, Se0 2 , is readily 
>luble in hot water. 

Tellurium.—The element dissolves in hot concentrated hydrochloric acid, 
n dilution of the solution a precipitate of H 2 Te0 3 -Te0 2 occurs. Treated 
jith concentrated nitric acid or aqua regia H 2 Te0 4 forms. With sulphuric 
3 id the compound H 2 Te0 3 forms and S0 2 is evolved. The element dis- 
[)lves in concentrated potassium cyanide, from which solution concentrated 
ydrochloric acid precipitates all of the tellurium. Tellurium is insoluble 
l carbon disulphide. The oxides TeO and Te0 2 are soluble in acids, Te0 3 

not readily soluble. All the oxides dissolve in hot potassium hydroxide 
plutions. 

Selenium and tellurium appear with the hydrogen sulphide subgroup ele¬ 
ments in the ordinary course of qualitative analysis. The acid solution of the 
material is treated cold with H 2 S, as the lemon-yellow SeS, formed in a cold 
mlution is more readily soluble in alkaline sulphide solutions than the orange- 
ellow SeS 2 precipitated from hot solutions. Although only a partial separa- 
on takes place the extract will contain sufficient selenium, if present in the 
, imple, to give a qualitative test. By precipitation from an acid solution by 
[ 2 S, selenium and tellurium are separated from members of subsequent groups. 
Tie sulphides precipitated are extracted with sodium or ammonium sulphide 
nd the extract examined for selenium and tellurium. 



306 


QUALITATIVE ANALYSIS 


DETECTION OF SELENIUM 

General Procedure—The sodium or ammonium extract is acidified wi 
hydrochloric acid, whereby selenium together with the other members 
the group are precipitated. The washed and dried precipitate is mixed wi 
twice its weight in a flux containing equal parts of sodium carbonate ai 
nitrate, and the mixture added to an equal amount of the flux which has be 
previously fused. The fluid mass is poured on to a slab of porcelain and t 
cooled melt placed in a beaker and extracted with water, whereby selem 
telluric, molybdic and arsenic acids dissolve, stannic oxide, sodium an 
monate, gold and the platinum group remaining insoluble. The extra 
is treated with an excess of hydrochloric acid and boiled to redu 
sodium selenate, Na2Se04, to selenious acid, H 2 Se 03 . A reducing age 
such as sulphurous acid, ammonium sulphite, hydrazine sulphate or h 
droxylamine is added and the solution boiled. Selenium, if present, is pi 
cipitated in its red or brown colored metallic form. The red color darkens 
boiling. 

Selenium is an odorless and tasteless solid. Its vapor has a putrid hors 
radish odor. The element burns with a reddish-blue colored flame. 

Dissolved in concentrated sulphuric acid a fine green-colored solution 
obtained, from which solution selenium may be precipitated by dilution wi 
water, the suspended substance giving a reddish tint to the acid. 

Hydrochloric acid decomposes selenates with evolution of chlorine gas 
boiling. 

Barium chloride precipitates white BaSeC> 3 , soluble in dilute HC1, wh 
added to selenites, and white BaSe0 4 , insoluble in dilute HC1, when added 
selenates. 

Hydrogen sulphide produces no precipitate with a selenate. This reduce 
however, by heating with HC1, a lemon-yellow to an orange-yellow preci 
tate of SeS 2 is obtained. 

The gas passed into a solution of selenite gives an immediate precipi 
tion of the sulphide, SeS 2 . 

DETECTION OF TELLURIUM 

Tellurium dissolved in concentrated sulphuric acid the acid purple 
carmine. The color disappears on dilution. The mineral may be treat 
directly with hot concentrated sulphuric acid and the color obtained in presei 
of tellurium. 

Heated in a test-tube tellurium compounds sublime and fuse to colorle 
transparent drops of Te0 2 . 

Hydrogen sulphide precipitates metallic tellurium mixed with sulpl 









THE LESS COMMON ELEMENTS 


307 


hen passed into acid solutions containing the element. The precipitate 
^sembles SnS in appearance. It is readily soluble in (NH 4 ) 2 S. 

Tellurium burns with a greenish flame. 

Reducing agents added to acid solutions of tellurium precipitate black 
letallic tellurium. 

Tellurium compounds are not as readily reduced as are those of selenium. 
1 solutions having an acidity of over 80 per cent, S0 2 gas causes the precipita- 
on of metallic selenium alone. Upon dilution with an equal volume of water 
illurium is precipitated. A separation may be effected in this way. 

Tellurates boiled with HCl evolve chlorine gas and are reduced to H 2 Te0 3 . 
•ilution of the solution will cause the precipitation of Te0 2 (distinction from 

3 ). 

Potassium iodide added to a tellurite in dilute sulphuric acid solution 
. : 4) precipitates black Tel 4 , soluble in excess of Kl, 


TUNGSTEN 

L, at.wt. 184 . 0 ; sp.gr. 18 . 77 ; m.p. 3000° C.; oxides, W0 2 (brown) 3 W0 3 
(yellow); acids, H 2 WO 4 , ortho tungstic; H 2 W 4 Oi 3 , meta tungstic. 

Tungsten occurs principally as wolfram, a tungstate of iron and manganese 
7 eW0 4 -Mn0 4 ), and as scheelite, a tungstate of calcium (CaW0 4 ). The best 
mcentrate of hand-picked material contains 70 to 74 per cent tungsten in 
^rms of its oxide, W0 3 . 

The element is met with in alloys—ferro-tungsten, silico-tungsten, tung- 
,en steels containing as much as 10 to 20 per cent of the metal, used for 
taking high-speed, self-hardening cutting tools; tungsten powder; alkali 
mgstates for mordanting purposes; tungstic oxide, W0 3 ; tungsten electric 
gift filaments, etc. 

For solution of the sample the following facts should be kept in mind 
| igarding solubilities. 

The metal is practically insoluble in HCl and in H 2 S0 4 . It is slowly 
jttacked by HN0 3 , aqua regia and by alkalies. It is readily soluble in a 
pixture of HN0 3 and HF ( = WF 6 or WOF 4 ). 

f Oxides—W0 2 is soluble in hot HCl and in hot H 2 S0 4 (=red sol.), also in 
fiOH (red sol.). The oxide W0 3 is scarcely soluble in acids, but is readily 
Dluble in KOH, K 2 C0 3 , NH 4 OH, (NH 4 )C0 3 , (NH 4 ) 2 S Z . Both the acid 
lid the alkali solutions deposit the blue oxide on standing. 

, Acids. Ortho tungstates.—A few are soluble in water and in acids. The 



308 


QUALITATIVE ANALYSIS 


alkali salts only slightly soluble. The meta tungstates are easily soluble 
water. Tungstates are precipitated from alkali salts by dilute H 2 SO 4 , HC 
HN0 3 , H 3 PO 4 (aqua) as yellow W0 3 -H 2 0 or white W0 3 -2H 2 0. Me 
tungstates are not precipitated by cold acids, but are precipitated by boilir 
and by long standing. 

Solution of Minerals. Fusion Method.—The material may be opened 01 
by fusion with alkalies or alkaline carbonates, or by solution in mixtures 
acids of which hydrofluoric acid is a constituent. 

Compounds of Tungsten, (a) Soluble.—Dioxydichloride, W0 2 C1 2 , yelkn 
tungstic acid (meta), H 2 W 4 0i3, yellow. 

( 1 b ) Decompose or are Insoluble.—Bromides, WBr 2 , WBr s , blue black 
violet brown; chlorides, WC1 2 , WC1 4 , WC1 5 , WC1«, steel gray to black; oxide 
W0 2 , brown; W0 3 , yellow; Sulphides, WS 2 , dark gray, WS 3 , black (s( 
alkalies, alk. sulphides). 


DETECTION 

Minerals.—The finely powdered material is fused with about six times i 
weight of potassium hydroxide in a silver or nickel crucible. (Fusion wi 
Na 2 C0 3 or with KHS0 4 in platinum will also decompose the materia 
The cooled mass is extracted with hot water and filtered. The solution 
treated with about 25 cc. of dilute hydrochloric acid and boiled. The pi 
cipitate formed may contain antimony, molybdenum, niobium, silica, ta 
talum, tin and tungsten. This is filtered and the moist residue treated wi 
a solution of yellow ammonium sulphide. Antimony, molybdenum, tin ai 
tungsten pass into the filtrate, niobium and tantalum remain on the filtt 
The ammoniacal sulphide extract is acidified with hydrochloric acid and boile 
The precipitate is filtered and washed with a little hydrochloric and niti 
acids. Antimony, molybdenum and tin pass into the filtrate, while tungst< ! 
and sulphur remain on the filter. Tungsten is now confirmed as follov 
portions of the precipitate being taken: 

1. The residue is suspended in dilute hydrochloric acid and a piece of zir 
aluminum, or tin placed in the solution. In the presence of tungsten a bh 
colored solution or precipitate is seen, the color disappearing upon dilutt 
with water. 

2. A portion of the precipitate is warmed with ammonium hydroxide a: 
the extracts absorbed with strips of filter paper. 

(a) A strip of this treated paper is moistened with dilute hydrochloric ac 
and warmed. In the presence of tungstic acid a yellow coloration is product 

(b) A second strip of paper is moistened with a solution of stanno 
chloride. A blue color is produced in the presence of tungsten. 








THE LESS COMMON ELEMENTS 


309 


(c) A third strip dipped into cold ammonium sulphide remains unchanged 
intil warmed, when the paper turns green or blue if tungsten is present. 

Iron, Steel and Alloys.—These decomposed with strong hydrochloric acid 
ollowed by nitric acid leave a yellow residue in the presence of tungsten. If 
:his residue is digested with warm ammonium hydroxide and the extract 
evaporated to dryness a yellow compound, W0 3 , will remain if tungsten is 
present. This oxide may be reduced in the reducing flame in the blue-colored 
exide. 






310 QUALITATIVE ANALYSIS 


RARER ELEMENTS OF THE AMMONIUM SULPHIDE GROUP 

CERIUM AND THE OTHER RARE EARTHS 


Group* 

Symbol 

At. Wt. f 

Sp. Gr. ' 

i 

M. P. 

Oxides 

Yttrium . 

. Yt 

88.7 

3.800 

1250 

Yt 2 0 3 

Erbium . 

. Er 

167 7 

4.770 


Er 2 0 3 , Er 2 0 { 

Holmium . 

. Ho 

163.5 



Thulium . 

. Tm 

168 5 



Tm 2 0 3 

Dysprosium . 

• Dy 

162.5 



Ytterbium . 

. Yb 

173.5 


1800 

Yb 2 O s 

(Neo-ytterbium) 






Lutecium . 

Lu 

175.0 




Europium . 

. Eu 

152.0 




Victorium . 


Discovery 

not confirm 

ed. 


Group 2: 






Terbium . 

. Tb 

159.2 



Tb 2 0 3 

Gadolinium . 

. Gd 

157.3 

1.310 


Gd 2 0 3 

Group 3: 





Cerium . 

. Ce 

140.25 

6.625 

950 

Ce 2 0 3 , Ce 2 0 6 

Lanthanum . 

La 

139.0 

6.163 


Tj9 oO o 

Neodymium . 

. Nd 

144.3 

6.544 

840 

-M-dCL g 

Nd 2 0, 

Praseodymium. . . . 

. Pr 

140.9 

6.544 

940 

Pr 2 0 3 

Samarium . 

. Sa 

150.4 

7.700 

1350 

Sm 2 0 3 

Scandium . 

. Sc 

44.1 


1300 

ScoO, 

Decipium . 

Discovery 

not confirm 

ed. 



* According to Bohm (Browning, “ Introduction to the Rarer Elements.”) 
t International atomic weights, 1916 . 


The estimation of the rare earths is not required, other than Cerium, at 
the present time except in a few special instances as the various elements have 
found but limited commercial applications. They have all been separated j 
from their native combinations, but only a few have been isolated and many 
are still believed to be combinations of elements. 

Cerium enters into the manufacture of Welsbach mantles; in the form of 
Ce 2 (S0 4 ) 3 it is used in the manufacture of aniline black; as oxalate, it is used 
in medicine, and as metal in alloys. 






















































THE LESS COMMON ELEMENTS 


311 


Yttrium is employed in the fabrication of Nernst lamp filaments and gas 
mantles. 

The most important ores which contain the rare earth elements are: 


Monazite, (Ce, La, Di, Th) x P 04 , 

raw 

material for Ce, La. 

Gadolinite, Be 2 FeY 2 Si 2 0 1 0 , 

a 

ii 

a 

Yt earths. 

Xenotime, YtPC>4, 

a 

ii 

a 

(( 

Yt 

Euxenite, R'^CNbO^• R 2 m (Ti0 3 ) 3 • 3/2H 2 0, 

a 

ii 


Yt “ 

Cerite, (Ca, Fe)(Ce0)(Ce 2 -30H)(Si0 3 ) 3 , 

a 

ii 

a 

Ce " 

Samarskite, R 3 "R 2 "'(Nb, Ta) 6 0 2 i, 

ii 

ii 

a 

Yt “ 

Yttrotantalite, R"R 2 '"(Nb, Ta) 4 0i5-4H 2 0, 

ii 

a 

a 

Yt “ 

Sipylite, complex, 

ii 

a 

a 

Yt 

Vi a 

Keilhauite, complex silicate, 




Yt 


In the formulas given above R" stands for any dibasic radical or element 
while R'" stands for any tribasic radical or element. 

Solution. 1. Fusion Method.— The finely pulverized sample is fused with 
sodium carbonate and the melt after cooling is extracted with cold water A 
sufficient quantity of hydrochloric acid to impart an acid reaction is added. 
The solution obtained is evaporated to dryness and baked to dehydrate the 
silica then treated with a little hydrochloric acid and after dilution with 
water filtered. Ammonia water is added to the solution in slight excess 
and the solution allowed to stand until the precipitate has settled. It is 
then filtered off, washed with cold water and dissolved in hydrochloric acid. 

■ • ■’ 1 ' ‘ - U1 — 1 — (ittnum 


All of the rare earths are then present in the solution as chlorides. 

^roup with carbonate precipitate.) . , . 

" 2 Acid Extraction.—Decomposition of the finely pulverized sample may 

be effected by mixing it with a sufficient quantity of sulphuric acid to make a 
paste and then heating the mass, slowly at first and then gradually increasing 
the heat to dull redness when fumes of S0 3 appear. After cooling, the mass 
is extracted with cold water and the metals of the H 2 S group removed m the 
usual way. The rare earths are then present in the solution as sulphates and 
may be separated by one of the methods detailed below. 

3 Decomposition by Means of Hydrofluoric Acid.-Samarskite and 
euxenite in the finely powdered state are moistened with ™JZt 

of water and twice as much fuming hydrofluoric acid. The attack takes 
place in a few seconds. When the violent action is over the solution is evap¬ 
orated to dryness on the steam bath, taken up with water (30 to 40 cc. for a 
S-gram sample) and the contents of the dish filtered and washed. The 
mineral is then divided into two portions, the filtrate containing all the 
metallic acids, iron and manganese, the insoluble portion containing all the 
rare earths and uranic acid. 







312 


QUALITATIVE ANALYSIS 


The difficulty of attack increases in proportion to the amount of tantalic 
acid present in the sample. The rare earths are then extracted from the 
incoluble portion by one of the methods previously mentioned. Fusion with 
sodium carbonate is preferred. 

RARE EARTH GROUP SEPARATIONS 

Separation of the rare earths from iron, aluminum and thorium may be 

effected by adding sodium fluoride to the hydrochloric acid solution of the 
Iron Group which has been precipitated as hydroxide. The precipitate, which 
consists of the double fluorides of the rare earths and thorium, is washed 
thoroughly and evaporated with sulphuric acid on the sand bath to decompose 
the fluorides. This process removes the alkaline earths as insoluble sulphates. 
The excess acid is removed by fuming and the solution of the sulphates after 
diluting and warming is treated with sodium thiosulphate in solution. Tho¬ 
rium thiosulphate is precipitated. In solution are the sulphates of all the 
rare earths. 

Cerium, lanthanum, praseodymium, neodymium, europium and gado¬ 
linium may be separated from the other rare earths by adding a saturated 
solution of potassium sulphate to the sulphate or chloride solution of all of the 
rare earths. The above-mentioned elements form insoluble double salts. 

Scandium may be separated from yttrium by boiling a solution of the 
nitrates. A basic scandium nitrate is first precipitated. 

Yttrium Group.—Barium carbonate forms no precipitate in the cold, hence 
the elements comprising same may be separated from aluminum iron, chro¬ 
mium, thorium, cerium, lanthanum, praseodymium, and neodymium by this 
means. 

Yttrium Group.—The precipitation of the group as hydroxides is not 
affected by the presence of tartaric acid. Hence the members may be thus 
separated from aluminum, glucinum, thorium, zirconium, and iron. 

Praseodymium, neodymium, lanthanum, and samarium may be separated 
from each other by the fractional precipitation of a dilute solution of the 
nitrates with a very dilute solution of ammonia water (1 gram of NH 3 in 500 
cc.). The first precipitates are rich in samarium; the didymiums come down 
next and the lanthanum in the last portions. By a continual repetition nearly 
pure salts may be obtained. 

Besides the separations mentioned above the group members may be freed 
from each other by various other methods, as for example: 

(1) Fractional crystallization of the picrates. 

(2) Fractional crystallization of the double magnesium nitrates. 

(3) Fractional precipitation of the oxalates in a nitric acid solution,"etc. 


THE LESS COMMON ELEMENTS 


313 


DETECTION 


The samples having been brought into solution by one of the procedures 
Dutlined, the elements may be precipitated as oxalates from an ammoniacal 
solution detected by one of the following tests: 

Spectroscopic.—Many of the rare earth’s elements have either character¬ 
istic spark spectrums or absorption spectrums and their presence may be 
detected by this means. 


Yttrium, 

no absorption spectrum; 

Erbium, 

gives “ 

U 

Ytterbium, 

no “ 

U 

Terbium, 

no 

U 

Cerium 

no 

a 

Lanthanum, 

no “ 

(( 

Samarium, 

gives “ 

n 

Scandium, 

no 

u 

Praseodymium, no 

u 

Neodymium, 

no 



gives brilliant spark spectrum. 


no spark spectrum. 


Cerium shows lines of greatest intensity in the arc spectrum at 4337.9, 
4527.5, 4386.9, 4594.1. In the spark spectrum at 4460.3, 4562.5, 4572.4, 
4594.b 4628.3. All of these lines are in the visible spectrum. 

The element having been brought into solution by one of the methods 
detailed above and separated from the base metals, silica and thorium may be 
isolated from the other rare earths by precipitation in a slightly acid solution 
with oxalic acid. The precipitate is allowed to settle twenty-four hours, 

I filtered, washed with water and ignited. The oxides are then dissolved in 
hydrochloric acid and precipitated as hydroxide by the addition of an excess 
of caustic potash. The precipitate, suspended in solution, is subjected to the 
action of chlorine gas which is bubbled through m a steady stream All of 
the rare earths except cerium are converted into the chlorides, while the 
latter remains as a reddish, gelatinous precipitate, ceric hydroxide — 


2Ce0 2 3H 2 0. 


eusoiiiU. . . , 

In the wet way cerium may be detected when in the form of cerium nitrate 
by boiling with lead peroxide and nitric acid. A deep yellow color is imparted 
to the solution, due to the formation of ceric nitrate. , 

Cerium may be detected by the addition of sodium hypochlorite to the 
solution of a colorless cerous salt. Red ceric hydroxide is precipitated The 
test may be confirmed by the chlorine gas evolved when the precipitate is 

dissolved in hydrochloric acid. . . 

Cerous salts are precipitated by fixed alkalies and are insoluble in excess. 



314 


QUALITATIVE ANALYSIS 


Tartaric acid hinders the precipitation. Ammonium sulphide also precipi¬ 
tates the hydroxide. Oxalic acid precipitates cerous oxalate, white, from 
moderately acid solutions. It is soluble in hot ammonium oxalate but pre¬ 
cipitated by dilution with cold water. 

Lanthanum may be detected by adding iodine to the washed precipitate, 
formed by the addition of ammonium hydroxide to a solution of its salts. A 
characteristic blue coloration results. 

Praseodymium, neodymium, may be detected by the reddish color of their 
solutions also by the rose-red or violet color imparted to a bead of microcosmic 
salt when heated in the flame of a blow pipe. 

Scandium.—The hydrochloric acid solution of a scandium salt, when boiled 
for thirty minutes with solid Na 2 SiFl 6 gives a precipitate which is free from all 
the other rare earths, the scandium taking the place of the sodium in the com¬ 
pound. 

Ytterbium may be detected by adding to a neutral solution H 2 Se0 3 *4H20. 
A white precipitate of Yb 2 (Se0 3 ) 3 , which is insoluble, results. 

Erbium.—In the flame test this earth gives an intense green light, 


GLUCINUM (BERYLLIUM) 

Gl, at.wt. 9.1; sp.gr. 1.85 20 °; m.p. > 960° C.; oxide, GIO. 

Glucinum occurs in the minerals beryl, euclase, davalite, chrysoberyl, 
helvite, leucophane, phencaite. 

The oxide, GIO, is soluble in strong sulphuric acid. It is decomposed by 
fusion with potassium fluoride. The freshly precipitated hydroxide, Gl(OH) 2 , 
is easily soluble in dilute acids, in alkalies and alkali carbonates and bicar¬ 
bonates. 

DETECTION 

General Procedure.—In the usual course of analysis glucinum will be 
precipitated by ammonia along with iron and aluminum hydroxides. Silica 
having been removed by evaporation to dryness of the acid solution of the 
substance, extraction of the residue with dilute hydrochloric acid and sub¬ 
sequent filtration; the members of the hydrogen sulphide group are precipi¬ 
tated from slightly acid solution by hydrogen sulphide. The filtrate is con¬ 
centrated to about 30 cc., and about 2 grams of sodium peroxide are added 
to the cooled liquid, which is now heated to boiling and filtered. Fe(OH) 3 
remains insoluble, if iron is present, while aluminum and glucinum dissolve. 
The filtrate is acidified with nitric acid, and ammonia then added in excess. 










THE LESS COMMON ELEMENTS 


315 


If a precipitate forms, alumina or glucinum or both are indicated. Glucinum 
hydroxide and aluminum hydroxide cannot be distinguished by appearance; 
the solubility of the former in sodium bicarbonate solution makes it possible 
to separate the two. The precipitate is dissolved in acid and the solution 
made almost neutral with ammonia. Solid sodium bicarbonate is added 
in sufficient amount to make the solution contain 10 per cent of the reagent 
and the mixture heated to boiling, then filtered. Alumina hydroxide remains 
on the filter paper and glucinum passes into the filtrate, in which it may be 
detected by diluting to ten volumes with water and boiling, whereupon 
glucinum hydroxide precipitates. 

Glucinum hydroxide, Gl(OH) 2 , is precipitated from neutral or acid solu¬ 
tion by ammonia, insoluble in excess (distinction from Al(OH) 3 ). It is pre¬ 
cipitated by sodium and potassium hydroxides, soluble in excess (separation 
from iron); if this solution is boiled Gl(OH) 2 is reprecipitated, Al(OH) 3 
remains in solution. Gl(OH) 2 is soluble in an excess of ammonium carbonate, 
Al(OH) 3 is insoluble. 


THORIUM 

Th, at.wt. 232.4; sp.gr. 7.7; 11.00; m.p. 1700°; oxides Th0 2 . 

The estimation of thorium is required chiefly in the fabrication of incan¬ 
descent gas mantles. Raw materials such as monazite P0 4 (Ca, La, Di Th) 
and thorite (ThSi0 4 ) are generally used. The former usually contains Rom 
2 to 4 per cent of thorium while the latter runs as high as 81.5 per cent, tho¬ 
rium nitrate in a rather impure state is the chief intermediate product The 
finished mantles generally contain 99 per cent Th0 2 and 1 per cent Ce0 2 . 

Solution.—“ A ” Silicates (as thorite, etc.) are decomposed by treatment 
with ten times their weight of fuming hydrochloric acid. This treatment 
usually suffices, but in cases where an insoluble residue still remains it is fused 
with ten times its weight of sodium carbonate in a large platinum crucible^ 
The fusion is dissolved in hydrochloric acid and added to the solution obtained 
from the first extraction. After the silica and the metals of the first group 
are removed in the usual way the solution is freed from H 2 S by boiling The 
thorium together with the other rare earths, calcium, magnesium etc, are 
then present as chlorides and the necessary separations made as detailed under 

gravimetric determination. . A ., 

“B” Phosphates (as Monazite, etc.) Fusion with Potassium Aci 
Sulphate. —0.5 gram of the finely pulverized material is mixed with 10 grams o 
potassium acid sulphate in a large platinum crucible, covered and heated until 









316 


QUALITATIVE ANALYSIS 


gentle fusion takes place and no further gas is given off. Then ignite over free 
flame for a few minutes, cool and treat with a little water and hydrochloric 
acid, until complete decomposition takes place. Boil for a few minutes, 
allow to cool and settle and decant off the clear liquid. The residue is treated 
with concentrated sulphuric acid and again extracted with water. 

DETECTION 

(1) By means of the spectroscope. Thorium shows lines of greatest 
intensity in the arc spectrum at 4863.3, and 4919.9. In the spark spectrum 
lines of greatest intensity at 3221.4, 3300.6, 4382.1, 4391.1. 

(2) By the addition of H 2 0 2 to a neutral solution of the nitrates containing 
ammonium nitrate. 

(3) By radio activity. Thorium compounds possess the power of con¬ 
tinually emitting Becquerel rays and radio active emanations. 


TITANIUM 

Ti, at.wt. 48.1; sp.gr. 4.5°; m.p. 1795° C. (±16°); oxides TiO, Ti 2 0 3 , 

Ti0 2 , TiO 3 . 

The element is widely distributed in minerals, soils, clays and titaniferous 
iron, FeTi0 3 . It is found in granite, gneiss, mica, slate, syenitic rocks, granu¬ 
lar limestone, dolomite,' quartz, feldspars and a large number of other minerals. 
The principal commercial minerals are: 

Umenite, FeTi0 3 , containing about 52.7 per cent Ti0 2 . 

Rutile, Ti0 2 , containing 90 to 100 per cent Ti0 2 . 

Titanite, CaTiSi0 5 , containing 34 to 42 per cent Ti0 2 . 

Perovskite, CaTi0 3 , containing about 60 per cent TiO a and 5 to 6 per 
cent Yt 2 0 3 . 

Titaniferous ores of variable titanic oxide content. 

By far the most important application of titanium at the present time is 
the use of ferrotitanium in the iron and steel industry. 

DETECTION 

The powdered ore is fused with potassium bisulphate, KHS0 4 , until effer¬ 
vescence ceases. The cooled mass is dissolved in dilute sulphuric acid by 
boiling. Hydrogen peroxide, H 2 0 2 , added to this titanium solution, produces 
a yellow to orange color, according to the amount of titanium present. Hydro¬ 
fluoric acid, or fluorides, destroys the color. Vanadium also produces this 


THE LESS COMMON ELEMENTS 


317 


olor with hydrogen peroxide, but the color is not destroyed by HF. The 
ellow color, according to Weller is due to Ti 03 formed. 

Morphine produces a crimson color with solutions of titanium in sulphuric 
,cid. 

Zinc added to hydrochloric acid solutions of titanium produces a blue color, 
in a fine violet solution. 

If sulphur dioxide, S0 2 , is passed into the solution of titanium to reduce the 
ron, and the slightly acid solution then boiled, yellowish white metatitanic 
,cid, TiO(OH) 2 , is precipitated. 

Bead Test on Charcoal. —A small portion of the powdered mineral heated 
,n charcoal with microscosmic salt and tin produces a violet-colored bead if 
itanium is present, 


URANIUM 

U, at.wt. 238.5; sp.gr. 18.7; m.p. <1850° C.; oxides U0 2 , U0 3 , 

(oxide U 3 0 8 , formed by ignition = U0 2 +2U0 3 ). 

1 The element occurs in the following minerals: 

Pitchblende, or uraninite, containing 40 to 90 per cent U 3 0 8 . 

3 Autunite, Ca(U0 2 ) 2 P 2 (V8H 2 0, contains 55 to 62 per cent U0 3 . 
Torbernite, Cu(U0 2 ) 2 -P 2 0 5 -8H 2 0, contains 57 to 62 per cent U0 3 . 
Carnotite, a vanadate of potassium and uranium, V 2 0 6 -U 2 0 3 -K 2 0-3H 2 0. 
Samarskite, a urano-tantalate of iron and yttrium, etc., 10 to 13 per cent 

J0 3 . . . . , . , • 

Fergusonite, a columbate of cerium, uranium, yttrium, calcium and iron. 
Nearly all the silicates, phosphates and zirconates of the rare earths contain 

1 iranium. , . .. , 

The element is used in the ceramic industry for producing yellow, brown, 
rray, and velvety-black tints. It produces canary-yellow glass. It is used as 
,! I mordant in dyeing of silk and wool. It also finds use in photography. The 
netal is used in cigarette-lighters and self-lighting burners. 

Solubility .—The element dissolves in hydrochloric and in sulphuric acids, 
ess readily in nitric acid. It is insoluble in alkaline solutions. 

The oxide, U0 2 , dissolves in nitric acid and in concentrated sulphuric 

! lC1 %he softs, UF, and U0 2 (HP0,)r4HA, are insoluble in water, but dissolve 
n strong mineral acids, 







318 


QUALITATIVE ANALYSIS 


DETECTION 

The mineral is warmed with a slight excess of nitric acid (1 :1) unti 
decomposition is complete. The solution is diluted with water and then ar 
excess of sodium carbonate added and the mixture boiled and filtered. Suffi 
cient nitric acid is added to neutralize the carbonate, and after expelling the 
CO 2 by boiling, sodium hydroxide is added to the filtrate. A yellow precipi 
tate is formed in presence of uranium. The precipitate is insoluble in an excess 
of the reagent, but dissolves in the ammonium carbonate. 

Uranous salts are green or blue and form green or bluish-green solutions 
from which alkalies precipitate uranous hydroxide, reddish brown, insoluble ir 
excess, but readily dissolved by ammonium carbonate. Uranous salts an 
strong reducing agents. 

Uranyl salts (U0 2 -R 2 ) are yellow. Alkali carbonates give a yellow pre¬ 
cipitate, soluble in excess. U0 2 is regarded as a basic radical, known as 
“uranyl.” The radical migrates to the cathode, upon electrolysis of a urany 
solution. Uranyl salts are more stable than uranous and are better known. 


VANADIUM 

V, at.wt. 61.0; sp.gr. 6.026; m.p. 1720° C.; oxides V 2 O f V 2 0 2 , V 2 0 3 , V 2 0 4 
V 2 0 5 ; vanadates—meta NaV0 3 , ortho Na 3 V0 4 , pyro Na 4 V 2 0 7 , tetri 
Na 3 HV 6 Oi7, hexa Na 2 H 2 V 6 0 17 . 

The materials in which the estimation of vanadium is desired may be sur¬ 
mised from the following facts: Industrial application. Vanadium is used ir 
special iron and steel alloys. It increases the strength of steel as well as the 
compression power, without loss of hardness, and increases the resistance tc 
abrasion; hence vanadium steels are used in locomotive and automobile 
cylinders, pistons, bushings and in all parts of machines subject to jar. It 
is used in high-speed tools, vanadium bronzes for gears, trolley wheels, etc 
It is used in indelible inks, and in the form of alkali vanadates and hypo- 
vanadates it serves as a mordant for aniline black on silk, for calico printing 
and like uses. Vanadium salts are used in ceramics where a golden glaze is 
desired. 

The element occurs widely distributed in minute quantities. It is found ir 
iron ores, hence occurs in blast-furnace slags as the oxide, V 2 0 6 . The principal 
ores are: 

Patronite, a sulphide of vanadium containing 28 to 34 per cent V 2 0 6 
associated with pyrites and carbonaceous matter; the principal source o) 
vanadium. 







THE LESS COMMON ELEMENTS 


319 




Vanadinite, (PbCl)Pb 4 (V0 4 )3, containing 8 to 21 per cent V 2 0 5 . 

Carnolite , K 2 0-2U0 2 -V 2 0 5 -3H 2 0, contains 19 to 20 per cent V 2 0 5 . 
Descloizite, (PbZn) 2 NV0 5 , contains 20 to 22 per cent V 2 0 5 . 

Roscoelite, a vanadium mica with variable composition. 

Eusynchite, contains 17 to 24 per cent V 2 0 5 . 

Cuprodescloizite, (PbZnCu) 2 (0H)V0 4 , contains 17 to 22 per cent V 2 0 5 . 
Caldorolborthite , (CuCa) 2 (0H)V0 4 , contains 37 to 39 per cent V 2 0 4 . 
Vanadium occurs in ores of copper and lead, it is present in certain clays 
nd basalts, in soda ash, phosphate soda, and in some hard coals. 

Solubility.—In decomposition of the material for analysis the following 
icts regarding the solubility of the metal, its oxides and principal salts, will 
•e helpful: 

Element— The metal is not attacked by aqueous alkalies, but is soluble by 
usion with potassium or sodium hydroxide, and sodium carbonate containing 
.otassium nitrate. It is insoluble in dilute hydrochloric and sulphuric acids, 
t dissolves in concentrated sulphuric acid and in dilute and concentrated nitric 
tcid forming blue solutions. 

Oxides.— V 2 0 2 is easily soluble in dilute acids, giving a lavender-colored 

lolution. , . . .... ... 

V 2 0 3 is insoluble in hydrochloric and sulphuric acids, and in alkah solutions. 

[t dissolves in hydrofluoric acid, and in nitric acid. 

V 2 0 4 is easily soluble in acids, forming blue-colored solutions. It dissolves 

n alkali solutions. . 

V 2 0 5 is soluble in acids, alkali hydroxide and carbonate solutions. Insol¬ 
uble in alcohol and acetic acid. _ .» . ,« 

Salts—Ammonium meta vanadate, NH 4 V0 3 , is slightly soluble in cold 
skater readily soluble in hot water. The presence of ammonium chloride 
renders the salt less soluble. The vanadates of lead, mercury and silver are 
difficultly soluble in water. These are dissolved, or are transposed by mineral 
acids, the vanadium going into solution; i.e., lead vanadate treated with 
sulphuric acid precipitates lead sulphate and vanadic acid passes into solution. 

detection 

Ammonium Sulphide or Hydrogen Sulphide passed into an ammoniacal 
solution of vanadium precipitates brown V 2 S„ soluble in an excess of alkali sul¬ 
phide and in alkalies, forming the brownish-red thio- solution, from which the 

sulphide may be reprecipitated by acids. ., , , . ., 

Reducing Agents —Metallic zinc, sulphites (S0 2 ), oxalic acid, tartaric acid, 
suear alcohol, hydrogen, sulphide, hydrochloric acid, hydrochromic and 
hydriodic acids (KI) reduce the acid solutions of vanadates with formation 





320 


QUALITATIVE ANALYSIS 


of a blue-colored liquid. (See Volumetric Methods.) Reduction is hastened 
by heating. 

Hydrogen Peroxide added to a cold acid solution of vanadium produces a 
brown color , changing to blue upon application of heat. 

Solid Ammonium Chloride added to a neutral or slightly alkaline solution 
of a vanadate precipitates the colorless, crystalline salt, NH 4 V0 3 , insoluble in 
ammonium chloride. The ammonium metavanadate ignited is decomposed, 
ammonia volatilizing and the red pentoxide of vanadium remaining as a 
residue. 

The colorless ammonium vanadate solution becomes yellow when slightly 
acidified. Acids produce a red color when added to the solid salt. 

The oxide , V 2 0 5 , is distinguished from Fe%Oz by the fact that it fuses very 
readily with the heat of Bunsen burner, whereas the oxide of iron, Fe 2 0 3 , is 
infusible in the heat of a blast lamp. M.p. Vs0 6 = 658° C.; m.p. Fe 2 0 3 = 
1548° C. 

Comparison of Vanadium and Chromium Salts.—Vanadium, like Chro¬ 
mium, forms a soluble salt upon fusion with sodium carbonate and potassium 
nitrate or with sodium peroxide. The solution of vanadates and of chromates 
are yellow or orange; the color of the chromate becomes more intense when 
strongly acidified, whereas that of the vanadate is reduced. The yellow color 
of the vanadate solution is destroyed by boiling with an excess of alkali, but 
may be restored by neutralizing the alkali with acid. The chromate color 
is not destroyed. (Yellow with alkalies, orange in acid solution.) Silver 
nitrate produces a dark-maroon precipitate with a soluble chromate and an 
orange-colored precipitate with a vanadate; mercurous nitrate produces a 
red-colored precipitate with chromates and a yellow with vanadates. Vana¬ 
dates are also distinguished from chromates by the reduction test: reducing agents 
such as a soluble sulphite, or sulphurous acid added to acid solutions, form a 
blue-colored liquid with vanadates and a green color with chromates . Ammonium 
hydroxide added in excess to the cold reduced solutions gives a brown color, 
or a brown to dirty green precipitate with vanadium , and violet or lavender 
color or a light green-colored precipitate with chromium , depending upon the 
concentration of the solutions. Hydrogen peroxide added to the reduced cold 
acid solutions changes the vanadium blue to reddish brown; the chromium 
green remains unchanged. 

Detection of Vanadium in Steel.—Five grams of the sample are dissolved 
in dilute nitric acid, the nitrous fumes boiled off, the solution cooled, and an 
excess of sodium bismuthate added. After filtering through an asbestos filter 
an excess of concentrated ferrous sulphate solution is added, and the solution 
divided into two equal parts in test tubes. To one portion 10 cc. of hydrogen 
peroxide are added and to the other 10 cc. of water. If vanadium is present 



THE LESS COMMON ELEMENTS 


321 


e peroxide solution will show a deeper color than the untreated solution, 
deep red color is produced with high vanadium steels and a brownish-red 
th low. Since titanium also causes this color, it would interfere, if it were 
t for the fact that the color produced with titanium is destroyed by hydro- 
loric acid and fluorides, whereas that of vanadium is not. In presence of 
anium, 5 cc. of hydrofluoric acid are added to the treated sample. 

The brown color produced by hydrogen peroxide, with vanadium solutions, 
11 remain in the water portion when shaken with ether. The ether layer is 
lored a transient blue in presence of chromium. 

Reduction with zinc is rapid with vanadates, much less vigorous with 
romates. V 2 0 5 reduced to V 2 0 2 , color changes to blue, green, lavender and 
lally violet, S0 2 or H 2 S reduces V 2 0 6 to V a CL, V 2 0 2 forms vanadyl salts. 


ZIRCONIUM 

Zr, at.wt. 90.6; sp.gr. 4.16; m.p. 1700°±C.; oxides Zr0 2 , Zr0 3 . 

The determination of zirconium is required in minerals, artificial gems, 
candescent gaslight mantles, firebrick, enamels, glass and various salts of the 
ineral acids. The chief source of zirconium is the mineral zircon (ZrSiO*) 
id its valuable modifications as hyacinth. Zircon contains from 60 to 67 
*,r cent of Zr0 2 . 

( Solution of Sample: 

A. Materials Containing a Large Amount of Silica 
Decomposition by Hydrofluoric Acid— Five grams of the finely powdered 
mple are treated in a large platinum dish with 50 cc. HFand 50 cc. of H 2 SO 4 . 
Ten the violent action has ceased the solution is evaporated first on the steam 
ith to expel the HF and then on a sand bath till fumes of SO 3 are given off. 
he residue is taken up with water. This usually effects complete solution 
the sample. If, however, an insoluble residue still remains, it is filtered off, 
ashed with cold water, ignited in platinum, and fused with 10 parts by 
eight of potassium acid sulphate. The cooled fusion is dissolved by boiling 
ith 20 per cent HC1. All the zirconium will now be in solution. 

B. General Method for Minerals, Oxides, etc. 
Decomposition by Fusion with an Alkali Carbonate. —Two grams of the 
lely pulverized sample are fused with 10 grams of Na 2 C0 3 (free of sulphur) 
id \ gram of KN0 3 in a large platinum dish. The melt is taken up in water 
id if manganese is present a few drops of alcohol are added to reduce the 






322 


QUALITATIVE ANALYSIS 


manganate to the manganous condition. The solution is filtered and the 
residue washed with dilute NaOH solution. The filtrate then contains all the 
silica as sodium silicate, while the residue contains all the zirconium, barium, 
etc. 


DETECTION 


The zirconium having been brought into solution by one of the methods 
outlined may be distinguished: 

(1) By the addition of sodium phosphate to a slightly acid solution. A 
white precipitate which is difficultly soluble in hydrochloric acid is character¬ 
istic of zirconium. 

(2) By its solution in hydrochloric acid coloring turmeric paper orange 
Titanium, however, colors it brown, and is apt to mask the color due t( 
zirconium when both are present, hence it is necessary to reduce the titaniun 
by the addition of a few pieces of zinc. Reduced titanium does not coloi 
turmeric paper, but it oxidizes rapidly, hence the test should be made a: 
quickly as possible. Boric acid also produces a yellow color with turmerii 
paper, but both elements are met with in the same sample on very rare occa 
sions only. 

(3) From alumina by the solubility of its carbonate in an excess of an alkal 

carbonate. The solution from ammonium carbonate if boiled precipitate, 
zirconia. i 

(4) From glucinum by the insolubility of its hydroxide in ammoniun 
chloride. Glucinum hydroxide dissolves readily in the reagent. 

(5) By spectroscopic methods. Zirconium shows lines of greatest intensity 
in the arc spectrum at 4687.9, 4739.6, 4772.5, 4815.8. and in the spark spectruc 
at 3999.1, 4149.4, 4209.4, 4380.1. 


THE RARE METALS OF THE ALKALI GROUP 

. 

Caesium, Cs, at.wt. 132.81; sp.gr. 1.87; m.p. 26.37°; b.p. 670° C.; oxide 
CS2O, CS2O2, CS2O3, CS2O4. 

Lithium, Li, at.wt. 6.94; sp.gr. 0.534; m.p. 186°; b.p. >1400° C.; oxide Li 2 C 
Rubidium. Rb, at.wt. 85.45; sp.gr. 1.532; m.p. 38.5; b.p. 696° C.; oxide 
Rb 2 0, Rb 2 0 2 , Rb 2 0 3 , Rb 2 04. 


Lithium occurs widely distributed, but in small quantities. Caesiur 
and Rubidium occur together in small amounts rather widely distributee 
They are found in the ash of plants and in certain minerals. 

Lithium is used commonly in the form of a benzoate; bromide; carbonate 
citrate; salicylate and chloride. Rubidium and caesium as chlorides. 







THE LESS COMMON ELEMENTS 


323 


DETECTION OF LITHIUM 

Bring the sample into solution as directed under preparation of the Solu- 
>n for Metals, Part IV, and separate the alkali chlorides from other con- 
ituents according to the standard procedure for removal of preceding groups, 
igest the dry chlorides with amyl alcohol or with a mixture of absolute 
sohol and ether, filter, and evaporate the filtrate to dryness. Moisten 
e residue with dilute hydrochloric acid and examine it in the spectroscope, 
bright red band and a faint orange line make up the flame spectrum of 
hium. These he between the sodium line and the red potassium line and 
e easily recognized 

Lithium salts impart a carmine-red color to the flame, which is obscured by 
dium, and by large amounts of potassium. But by the proper use of a color 
reen, the lithium flame may be recognized in the presence of large amounts 
sodium. 

Confirmation of the presence of lithium may be had by the formation of the 
aringly soluble lithium phosphate or lithium fluoride. 

DETECTION OF RUBIDIUM AND CAESIUM 
1 In the usual course of analysis, these rare elements are separated along with 
dium, potassium, and lithium from all other bases. In order to detect 
bidium and caesium, extract the dry chlorides of the alkali metals with a 
v drops of hydrochloric acid and 90 per cent alcohol. This will dissolve 
;ost of the rare alkalies along with some sodium and potassium. Evaporate 
e solution to dryness, dissolve in a very small amount of water, and add 
!loroplatinic acid solution. Rubidium, caesium, and potassium chloro- 
titinates will be precipitated. Filter and wash the residue repeatedly with 
s t water to remove the potassium salt, which is much more soluble than 
< bidium and caesium chloroplatinates. During this treatment, examine 
se residue from time to time in the spectroscope. As the rubidium and 
jesium salts are concentrated through washing, their spectra will gradually 
icome visible. 

Lithium. Dry Tests .—The flame is colored carmine-red by lithium salts. 
| Spectroscope shows a bright crimson line with a feeble orange line. 

I Wet Tests .—Carbonates and phosphates of sodium or potassium precipi- 
ti be, in solutions containing NaOH, lithium carbonate or phosphate. The 
It Its are soluble in ammonium salts. 

I Caesium and Rubidium are best studied by means of the spectroscope. 

gives orange-yellow and blue lines. Rb gives a and b lines in blue and 
eg in red, yellow, and green. 

SnCl 4 precipitates 2CsClSnCl 4 from cone, solutions of Cs salts. HC 4 H 6 0 6 
Iscipitates from cone, solutions of Rb salts white RbC 4 H 6 0 6 . 





Mendeleef’s Periodic System of the Elements 

Revised by the author 


324 


QUALITATIVE ANALYSIS 


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326 


QUALITATIVE ANALYSIS 


Reagents in Solution 


Acids 



Sp. Gr. 

Concentra¬ 
tion, %. 

Approxima¬ 
te ormalit 
Factor. 

Inorganic 




Hydrochloric, saturated HC1 

1.20 

39.11 

12.9N* 

Hydrochloric, concentrated HC1 

1.12 

24.00 

8 .ON 

Hydrochloric, dilute HC1 

i.03 

7.15 

2.ON 

Nitric acid, fuming HN0 3 

1.42 

69.80 

15.7N 

Nitric acid, concentrated HN0 3 

1.20 

32.05 

8 .ON 

Nitric acid, dilute HN0 3 

1.07 

12.30 

2.ON 

Sulphuric acid, concentrated H 2 SO< 

1.84 

95.60 

36.ON 

Sulphuric acid, dilute H 2 S0 4 

1.12 

17.00 

4.ON 

Sulphurous acid, saturated solution 




of SO 2 in water 

— 

— 

3.ON 

Organic 




Acetic acid, glacial 

1.058 

99.0 

17.6N 

Acetic acid, dilute 

1.030 

22.0 

4.ON 

Tartaric acid, 150 gm. per liter 

— 

— 

2.ON 

Alkalies 




Ammonium hydroxide, NH 4 OH 

0.90 

28.33% NH 3 

15.ON 

Ammonium hydroxide, dilute 




NH 4 OH 

Potassium hydroxide, KOH, 281 

0.97 

7.05% NH 3 

4.ON 

gm. per liter 

— 

— 

4.ON 

Sodium hydroxide, NaOH, 178 gm. 




per liter 

— 

— 

4.ON 


* A normal solution of a reagent contains in a liter that proportion of its molecuh 
weight in grams which corresponds to one gram of available hydrogen or its equivalen 
N-HC1 contains its molecular weight (36:47 g.) HC1 per liter of solution. N • H 2 SO 4 contaii 
one-half of its molecular weight, i.e., 98.08-7-2 =49.04 g., HiSCh per liter of solution. 
















THE LESS COMMON ELEMENTS 

Salts 

327 


Grams per Liter. 

Approximate 

Normality. 

] Ammonium acetate, NH 4 C 2 H 3 O 2 

308 

4 N 

1‘Ammonium carbonate, (NH 4 ) 2 C 0 3 

78 

add 40 cc. NH 4 OH 

2 N 

Ammonium chloride, NH 4 C1 

107.1 

2 N 

“Ammonium molybdate, (NH 4 ) 2 Mo 04 

98 

N 

Ammonium oxalate, (NH 4 )2C 2 0 4 

saturated 

N 

Ammonium sulphate, (NH 4 ) 2 SO 4 

66 

N 

Ammonium sulphide, (NH 4 ) 2 S 

— 

4 N 

* Ammonium poly sulphide, (NH 4 ) 2 S X 

— 

— 

Ammonium tartrate, (NH 4 ) 2 C 4 H 40 6 

(NH 4 OH+ 

H 2 C 4 H40 6 


Barium carbonate, BaC0 3 

solid diff. in H 2 0 

— 

Barium chloride, BaCl 2 -2H 2 0 

122.2 

N 

Barium hydroxide, Ba(OH) 2 

sat. sol. 

i N 

Calcium chloride, CaCl 2 

55.6 

N 

Calcium hydroxide, Ca(OH) 2 

sat. sol. 

T2 N 

Calcium sulphate, CaS0 4 

sat. sol. 

Ts N 

Cobalt nitrate, Co(N0 3 ) 2 . 6H 2 0 

62.3 

* N 

Ferric chloride, FeCl 3 -6 H 2 0 

91 

(add 5 cc. HC1) 

N 

*Ferrous sulphate, FeS0 4 -7 H 2 0 

139 

(add 20 cc. H 2 S0 4 
+50 gm. (NH 4 ) 2 
SO 4 ) 

N . 

Lead acetate, Pb(C 2 H 3 0 2 )2*3 H 2 0 

185.5 

(add HC 2 H 3 0 2 
till acid) 

N 

*Magnesia mixture 

sat. sol. 

N 

Mercuric chloride, HgCl 2 , 

\ N 

1 Platinic chloride, H 2 PtCl$ 

10.66 

To N Pt 

| Potassium bromide, KBr 

59.6 

\ N 

Potassium chromate, K 2 Cr0 4 

97.3 

N 

* See “ Preparation of Special Reagents.” 














QUALITATIVE ANALYSIS 


328 


Salts 



Grams per Liter. 

Approximate 

Normality. 

Potassium cyanide, KCN 

65.2 

N 

Potassium dichromate, K 2 Cr 2 0 7 

73.8 

N 

Potassium ferricyanide, K 3 Fe(CN) 6 

11.0 

To N 

Potassium ferrocyanide, K 4 Fe(CN) 6 

10.6 

iV N 

Potassium iodide, KI 

83.1 

h N 

Potassium nitrite, KN0 2 

sat. sol. 

24 N 

Potassium permanganate, KMnO 

15.8 

h N 

Potassium sulphate, K 2 S0 4 

174 

N 

Potassium thiocyanate, KSCN 

48.6 

h N 

Silver nitrate, AgN0 3 

42.5 

h N 

Silver sulphate, Ag 2 S0 4 

sat. sol. 

ih N 

Sodium acetate, NaC 2 H 3 0 2 

328 

4 N 

*Sodium carbonate, Na 2 C0 3 , fused 

212 

4 N 

Sodium chloride, NaCl 

29.3 

h N 

*Sodium cobalt nitrite, Co(N0 2 ) 3 -3 NaN0 2 

— 


Sodium phosphate, Na 2 HP0 4 -12 H 2 0 

119 

N 

*Stannous chloride, SnCl 2 cone, and dil. 

— 

_ 

Zinc sulphate, ZnS0 4 -7 H 2 0 

140 

— 


* See “ Preparation of Special Reagents.” 


Other Solutions.—Amyl alcohol, C 6 HnOH; bromine water, Br; chlorine 
water, Cl; carbon disulphate, CS 2 ; ethyl alcohol, C 2 H 5 OH; indigo, 2(C 8 H 6 ON): 
hydrogen peroxide, H 2 0 2 , 3 per cent; methyl alcohol, CH 3 OH. 

Solid Reagents 

Aluminum foil, Al. 

Ammonium nitrate, NH 4 N0 3 . 

Ammonium sulphite, (NH 4 ) 2 S0 3 -H 2 0. 

Barium hydroxide, Ba(OH) 2 -8 H 2 0. 

Borax, Na 2 B 4 O 7 10 H 2 0. 

Calcium carbonate, CaC0 3 (marble). 

Copper foil, Cu. 

Cotton, absorbent. 

Ferrous sulphate, FeS0 4 -7 H 2 0. 

Glass wool. 










THE LESS COMMON ELEMENTS 


329 


Iron filings, nails, or wire. 

Lead acetate, Pb(C 2 H 3 0 2 )2, 3 H 2 0. 

Lead dioxide, Pb0 2 . 

Oxalic acid, H 2 C 2 0 4 -2 H 2 0. 

Potassium carbonate, K 2 C0 3 . 

Potassium chlorates, KC10 3 . 

Potassium cyanide, KCN. 

Silver nitrate, AgN0 3 . 

Sodium ammonium phosphate, NaNH 4 HP0 4 -4 H 2 0. 

Sodium carbonate, Na 2 C0 3 . 

Sodium and potassium nitrate, Na 2 C0 3 +KN0 3 . 

Sodium hydroxide, NaOH. 

Sodium sulphite, Na 2 S0 3 *7 H 2 0. 

Tartaric acid, H 2 C 4 H 4 06. 

Tin foil, zinc foil, and granulated tin and zinc. 

Preparation of Special Reagents 

Ammonium acetate may be prepared by neutralizing 100 cc. acetic acid 
with NH 4 OH (about 96 cc.). 

Ammonium Carbonate. —Dissolve in 80 cc. NH 4 OH(0.90)+500 cc. H 2 0, 
and dilute to one liter. 

Ammonium Molybdate. —Dilute 150 cc. NH 4 OH to 300 cc., add 72 g. 
molybdic oxide; pour slowly into solution of dilute nitric acid (250 cc. HN0 3 , 
"sp.gr. 1.42 to 500 cc. water). Allow to stand several days in warm place, 
and decant clear supernatant liquid for use, diluting to one liter, 
if Ammonium Sulphide— Saturate 150 cc. strong NH 4 OH with H 2 S, add 150 

) cc. NH 4 OH, and dilute to one liter. 

Ammonium Polysulphide.— Add to a portion of the above a little free 
sulphur. 

Bromine Water. —To 50 g. KBr dissolved in 500 cc. H 2 0, add 10 cc. Br. 
Shake until dissolved. 

Chlorine Water. —Saturate water with Cl gas. Keep in dark bottle. 

Cleaning Mixture. —Dissolve 50 g. of powdered K 2 Cr 2 0 7 in about 200 cc. of 
warm water; cool. Pour into cool solution with constant stirring about 250 
cc. H 2 S0 4 (cone.). 

Ferrous Sulphate.— Oxidation may be prevented by adding iron wire or 
nails to solution. 

Indigo Solution. —Dissolve in fuming H 2 S0 4 , keeping cold, 1 part indigo, 
powdered, to 5 parts acid. Allow to stand several days, then pour into 20 
i parts of water. 








330 


QUALITATIVE ANALYSIS 


Magnesia Mixture.—50 g. MgS0 4 and 75 g. NH 4 C1 dissolved separatel 
in water; mix and add 300 cc. strong NH 4 OH. Dilute to one liter. 

Nessler’s Reagent.—Dissolve 20 g. of KI in 50 cc. of water; add 32 g. Hg 
Dilute to 200 cc., and add 134 g. of KOH that has been dissolved in 260 cc 
of water. 

Phenolsulphonic Acid.—Dissolve about 24 g. phenol in 150 cc. H 2 S0 4 cone 
add 15 cc. of water. Keep in dark glass bottle. 

Sodium Cobaltic Nitrite.—Dissolve 100 g. NaN0 2 in 300 cc. H 2 0; ad< 
acetic acid to acid reaction, and then 10 g. Co(N0 3 )2. Allow to stand severa 
hours and filter. Solution will decompose. 

Stannous Chloride.—Dissolve 225 g. of SnCl 2 in 500 cc. NH 4 C1; dilut 
to one liter. Place some fragments of metallic tin in the bottle containing th 
solution. 

Starch paste may be preserved by addition of a few drops of chloroform. 











INDEX 


acetic acid.... 

detection of. 

properties of. 

solubilities. 

tabulated tests of. 

test for nitrite. 

Acidity test of free acid in solution. 

Lcids. 

classification of. 

general characteristics. 

solubility of salts, rules for. 

solution, preparation of. 

systematic examination of. 

table of general tests. 

table of separations. 

dcohol flame tests for borate. 

Llizarine S test for aluminum. 

tlkali group. 

description of members of. 

separation of members. 

rare metals of. 

Ukaline earth group. 

description of members 
removal from alkalies. . 

separations. 

Alloys, analysis of.. 

aqua regia solution of. 

list of. 

nitric acid solution of. 

Aluminum. 

compounds of. 

detection of. 

properties of. 

reactions with reagents. 

separations from other elements.. 

tests for (see detection). 

Alpha benzildioxime test for nickel. 


PAGE 

..207-209 

. 209 

. 207 

.264 

.260 

. 159 

. 63 

. .154- 210 

. 154 

. 154 

. 232 

. 233 

.232 

. 235 

. 234 

. 193 

. 82 

..140-153 

. 140 

. 149 

. 322 

..125-139 

. 125 

. 152 

. 134 

..226-229 

. 228 

.228 

. 226 

. 81 

. 264 

82, 92, 246 

. 81 

. . ..92,346 
. . .109-123 

. 82 

. 90 


331 









































332 


INDEX 




PAG] 


Ammonia, detection and properties. ....143, 15 

solubility in water. ‘ i 

Ammonium acetate reagent, prep, of. 32' 

carbonate group, properties of. 12 

reactions. 12' 

tabulated tests. 25 j 

reactions with Al, Cr, Fe. 24 

Co, Ni, Kn, Zn. 34 

Ba, Ca, Sr. 25 

reagent. 32 

hydroxide, reactions w r ith aluminum. 24 

antimony. 24 

bismuth. 24 

cadmium.*.. 24 

chromium. 24 

cobalt. 24 

copper. 24 

lead. 24 

manganese. 24 

. magnesium. 25 

mercury.240, 24 

* nickel. 24 

iron. 24 

silver. 24 

separation of Al, Cr, Fe, from Co, Mn, Ni 

and Zn.120, 12 

tin. 24 

zinc. 24 

See also lab. exercises under groups on metals. 


molybdate, reagent. 32 

test for arsenic.52, 5 

test for phosphate. 19 

polysulphide, reagent. 32' 

solution of H 2 S group.60, 6 

see reactions and separations.56-6' 

test for cyanide. 17! 

sulphate, tests for Ba, Ca, Sr.135, 137, 251 

See ammonium carbonate group. 

sulphide group, descriptive. 8 

rare elements of. 31< 

separation of members.109-lit 

tabulated tests of. 24( 

reactions with Al, Cr, Fe. 24< 

Co, Ni, Mn, Zn. 241 

See exercise on elements. 91 

prep, of reagent. 32J 

sulphocyanate, detection of cobalt. 8,' 

tabulated tests of. 25S 

Amphoteric electrolyte, definition of. J 

Aniline sulphate, test for chlorate. 20J; 





















































INDEX 


333 


Lntimonic salts, distinct, from .. 

mtimonous salts, distinct, from -ic. 

reactions. * • • • • 

Lntimony, compounds of. 

I detection of. 

distinction from arsenic. 

property of. 

reactions. 

separations. 

tabulated reactions. 

Apparatus, cleaning of. 

Lqua regia, solution of alloys. 

solution of substances. 

Arsenate, distinction from arsenite. 

Arsenic acid.. 

compounds of. 

detection of. 

distinction from antimony. 

properties. 

reactions. 

tabulated tests. 

Arsenite, distinct, from arsenate. 

Arsenous acid, detection of. 

properties of. 

tabulated tests of. 

Asbestos filter. 

Atomic weights, table of. 

Barium acetate detection of chromium. 

carbonate reaction with Al, Cr, Fe. 

Co, Ni, Ma, Zn 

chloride group.. 

table of analysis. 

test for borate. 

test for chromate. 

test for fluoride. 

test for phosphate... 

test for sulphate. 

compounds of. 

detection, of. 

properties of. 

reactions . ..., . 


separations. 

tabulated tests. 

Baryta test for magnesium.' ' ...! V ' 

Basic acetate, method for separations of (NHi).S group meta s 


Benzidine acetate, test for gold . 
Benzoic acid, tabulated tests for 
Beryllium. See glucinum. 
Bettendorff, test for arsenic. 


PAGE 

. 50 

. 50 

. 69 

. 266 

.49, 69 

. 50 

. 49 

_69.244 

.74-77 

. 244 

. 23 

. 228 

. 223 

. 52 

. 184 

. 267 

_51,192 

. 50 

. 51 

68,244,254 
...244, 254 
....52,192 

. 192 

. 184 

...... 254 

. 22 

. 263 

. 83 

. 246 

. 248 

...155, 184 

. 198 

. 193 

. 195 

. 195 

. 196 

. 197 

. 268 

_126,129 

. 125 

_129, 250 

. 134 

. 250 

. 142 

. 122 

. 294 

. 260 

. 54 






















































334 


INDEX 


PAGB 

Bismuth, compounds of....... 269 

detection of.46, 24S 

properties of. 4 f 

reactions with. 57 , 24S 

separations. 6 ( 

tabulated tests. 242 

Black filter paper, test for fluoride. 188 

Blowpipe tests.16, 2It 

test for arsenic. 52 

bismuth. 4 (i 

cadmium. 47 

Borax bead tests.19, 218 

test for borate. 185 

Cr, Fe. 246 

Co, Ni, Mn, Zn.85, 88 , 89, 248 

cobalt. 103 

nickel. 106 

Boric acid, detection of.185, 193 

properties of. 184 

tabulated tests of. 254 

Boron compounds. 269 

Bromate, detection of. 173 

Bromide compounds detection. See bromine. 

Bromine, detection of. 173 , 177 

properties of. 172 

reactions with reagents. 177 

solubility. 269 

water, preparation of. 329 

Buchner funnel. 21 


Cadmium, compounds of. 269 

detection of. 47 , 242 

properties of. 47 

reactions with reagents. 59 , 242 

separations. 60 

tabulated tests. 242 

Calcium chloride reactions with acids.254-261 

test for fluoride. I 95 

compounds of. * . 270 

detection of. 127 , 250 

reactions with reagents. 131 , 250 

separations. I 34 

sulphate test for barium. 126 

oxalate. 209 

tabulated tests. 250 

Carbolic acid, tabulated tests for. 260 

Carbonate, tests for. I 64 

distinction from bicarbonate. 15 g 

Carbon, compounds of. 271 

detection of. i» 


















































INDEX 


335 


arbon, properties of. 

dioxide, detection of. 

solubility in water. 

disulphide, test for bromide. 

arbonic acid, tabulated tests of. 

arbon monoxide, detection of. 

asserole. 

lierium and the rare earths. 

compounds of. 

detection of. 

properties ot. 

solution of compounds of. 

Charcoal tests. 

Chemical equilibrium. 

reactions. See group. 

Chlorate, test for. 

Chloric acid, detection of. 

tabulated reactions. 

chloride, detection in presence of other halogens .... 
separations. Se chlorine. 

Chlorine, detection of. 

free, detection of. 

in presence of cyanate, cyanide, thiocyanate 

properties of. 

test for bromide. 

test for iodide. 

water, reagent. 

ZJhloroplatinic acid, test for ammonium. 


Chlorite, test for. 

Chromate action on antimonious salt 

test for barium. 

lead. 

Chromic acid and chromate, detection of. 

properties of. 

tabulated tests of. 

hydroxide. 

Chromium,compounds of. 

detection and properties.. . . 

reactions. 

separations. 


tabulated tests 


Citric acid, tests for. 

r Class-room reviews. See close of groups. 

Cleaning apparatus. 

mixture. 

Cobalt, compounds of. 

detection of. 

nitrate test for aluminum. 

ammonium and potassium. 

zinc. 


PAGE 

. 157 

. 158 

. 4 

. 173 

. 254 

. 158 

. 22 

.310 

. 271 

. 313 

. 310 

. 311 

. 216 

. 9 

. 171 

200, 203, 255 

. 255 

.171,181 

. 171 

.171,176 

. 171 

. 170 

. 177 

. 177 

. 329 

.147 

. 159 

. 50 

.126, 129 

..34,37,41, 162 

. 194 

. 185 

. 255 

. 185 

. 272 

. 83 

. 94 

. 109 

. 246 

. 260 

. 23 

. 329 

. 272 

.85,248 

. 93 

. 147 

.91, 108 




















































336 


INDEX 


Cobalt, properties of. 

reactions with reagents. 

separations. 

tabulated tests. 

test for ammonium. . . .. 

test for nitrite. 

Color indications of elements by H 2 S ppt. . 

reactions.. 

Combustion tube tests. 

Common ion effect. 

Complex ion, definition of.. 

Cone, platinum for filtering. 

Confirmatory tests for aluminum. 

chromium. 

cobalt. 

iron. 

lead. 

manganese. 

mercury. 

nickel. 

zinc. 

Copper, compounds of. 

detection of. 

group... 

properties of. 

reactions with reagents. 

separations. 

sulphate reactions with As, Sb, Sn 

tabulated tests. 

Crystalline, definition of. 

Curdy, definition of. 

Cyanide, tests for. 


PAG 
... 8 
101, 24 
...10 
...24 
...14 
... 16 
... G 


21 

1 


.... 2 
,... 9: 

.... 9i 
.... 10 ; 

. ... 10 < 
... 3' 

,... 10 < 
... 31 

... 10 ( 
... lOf 
... 27c 
.47, 242 
... 4£ 

... 47 

.58, 242 
... 6C 
244,245 
... 242 
2 
2 

164, 178 


Decantation, definition of. 2 

Definitions and chemical terms. 1 

Dichromate test for chloride.•. 175 

tests. See chromate. 

Dicyandiamidine sulphate test for cobalt. 85 

Digestion, definition of.'. 2 

Dimethylglyoxime test for nickel.gg t jq 6 

Diphenylamine test for nitrate. 201 205 

Diphenylcarbazide test for chromium. 84 

Dry tests.211-220 


Earths, rare. See cerium 
Electrolysis, definition of. 

Electromotive series. 

Elements, list of. 

Equation, definition of . . 
Erlenmeyer flask. 




















































INDEX 


337 


Itching, test for fluoride. 

Ither, test for chromium. 

Ivaporation, directions regarding. 

| 

"erne chloride, test for cyanide. 

ferrocyanide. 

phosphate. 

salicylate. 

thiocyanate. ... 

ferrocyanide test for sulphate. 

iron, distinction from ferrous. 

reactions with. 

reduction of. 

ferricyanide, detection of. 

reaction with ferrous iron. 

reactions with Al, Cr, Fe. 

Co, Ni, Mn, Zn . 

ferrocyanide, detection of. 

reactions with Al, Cr, Fe,. 

Co, Ni, Mn, Zn- 

test for iron. 

i'errous iron, oxidation of. 

preparation of solution of. 

reactions with. 

sulphate, reagent. 

test for ferricyanide. 

test for nitrate. 

test for platinum. 

film tests. 

filter, folding of. 

stand.. 

filtering, directions regarding. 

filtrate, definition of..' 

filtration, directions regarding. 

flame, color tests. 

oxidizing. 

reducing. 

structure of. 

tests, ammonium carbonate group.... 

for arsenic... 

Ba, Ca, Sr.,. 

barium. 

borate. 

calcium.. . 

copper. ....... . 

general. 

Li, K, Na. 

potassium... 

sodium. 

strontium. 


PAGE 

.187,195 

. 84 

. 22 

. 179 

. 179 

. ..'._ 196 

. 209 

. 180 

. 168 

. 87 

. 100 

. 101 

180, 181, 235 

. 99 

. 247 

. 249 

179, 181, 235 

. 247 

. 249 

. 87 

. 99 

. 98 

. 98 

. 329 

. 180 

. 203 

. 296 

. 18 

. 22 

. 21 

. 21 

. 2 

. 20 

. 19 

. 17 

. 16 

. 17 

. 126 

. 52 

. 250 

. 126 

. 184 

. 127 

. 48 

. 217 

. 253 

. 144 

. 145 

. 128 























































338 


INDEX 


PAGI 

Fleitmann test for arsenic. 54 

Flocculent, definition of. 5 

Fluoride, detection of. 19; 

method for detecting silicate. 16; 

Fluorine. 27,' 

detection of.187, 19; 

properties. 18f 

reactions with salts of. 19,' 

Fluosilicates, insoluble. / . 181 

Fluosilicic acid, test for barium. 12( 

Formaldehyde test for bismuth. 4( 

Formic acid, properties. 271 

tabulated tests. 26( 

test for platinum. 29( 

Free nitric acid, detection of. 201 

sulphuric acid, detection of. 19' 

Fundamental principles of analysis. 4 

Funnels, directions regarding. 2: 

Fusions, methods for refractory materials. 22' 

Fusion test for manganese. 10' 

Gallic acid, tests for. 261 

Gatehouse test for arsenic. 5' 

General procedures for detection. See element. 

Glucinum, compounds of... 271 

detection and properties. 31/ 

Gold, compounds of. :. 267, 27* 

detection and properties of. 29,' 

separation from H 2 S, group B. 7 ; 

tabulated reactions. 24,' 

Gooch crucible. 2. 

Granular, definition of. ; 

Groups, outline for separation of. 3 

reactions with.•.. 21 

Gutzeit test for arsenic.52, 5 ; 

Halogens, detection and separation of. 181 

Hanging drop test for fluoride. lg{ 

Heating substances.,. K 

Hydrazine, properties. 271 

Hydriodic acid, detection of. 174 , 17 ' 

properties of. 173 j 27( 

tabulated tests for. 251 

Hydrobromic acid, detection of. 173 , 17 ; 

properties of. 172 , 27( 

tabulated tests for. 251 

Hydrochloric acid, detection of. 171 , 175 , 25( 

^precipitation of Ag, Hg, Pb with. 3 ^ 

procedure for dissolving solids. 225 

properties of.170, 27C 




















































INDEX 


339 


PAGE 

[ydrochloric acid, solubility in water. 4 

tabulated tests for. 256 

test for HC1 group.28, 31, 33-44 

lead.24, 37 , 40 

iron. 87 

mercury.35,37,40 

silver....36, 38, 40 

ydrocyanic acid, detection of. 178 

properties of. 174 , 276 

tabulated tests for. 256 

ydroferricyanic acid, detection of. 180 

See also ferricyanide. 

properties of. 175 

tabulated tests for. 256 

ydroferrocyanic acid, detection of. 179 

See also ferrocyanide. 

, 1 

properties of. 175 

tabulated tests for. 256 

ydrofluoric acid, detection. See fluorine. 

method for refractory substances. 223 

properties. 276 

tabulated tests for. 256 

ydrofluosilicic acid, tabulated tests. 276 

ydrogen, property. 276 

solubility in water. 4 

chloride group, characteristics. 33 

reactions of group.. .37-39, 240 

separation of members. 40 

tabulated tests of. 240 

peroxide, test for chromium.84, 194 

test for nitrate. 206 

sulphide group, characteristics. 45 

detection of members.46-79 

separations. 60 

rare metals of. 293 

detection of. 163 

occurrence. 161 

properties. 162 

reactions with Ag, Hg, Pb..34, 35, 240 

Bi, Cd, Cu, Hg+ +.48, 242 

As, Sb.49, 51, 244 

Sn, Pt, Au. 245 

Fe. 246 

Co, Ni, Mn, Zn.91, 248 

test for antimony. 49 

arsenic. 51 

copper. 48 

lead. 34 

mercury. 35 

platinum... 296 























































340 


INDEX 


Hydrogen, sulphide test for rare metals Pt. gp. 

Se, Te, Mo 


Hydrolysis, definition of. 

of antimonic salts. 

bismuth salts. 

Hydrosulphuric acid, tabulated tests. 

See also hydrogen sulphide. 

Hydroxide method for separating Al, Fe, Cr from Co, Mn, Ni, Zn 

Hydroxylamine. 

Hypochlorite, detection of. 

Hypochlorous acid, detection. 

properties. 

tabulated tests. 

Hypophosphorus acid, detection and properties. 


Ignition tube tests. 

Indigo solution, reagent. 

test for chlorite. 

hypochlorite. 

Indium. 

Inorganic acids, tables of tests for. 

compounds. 

Insoluble chromium compounds. 

ferrocyanide, detection of. 

H 2 S subgroup A. 

reactions. 

tabulated tests of. 

silicate, detection of. 

substances, solution of. 

Interfering substances, (NH.O 2 S group. 

in nitrate test.. 

removal of from solution, 

Interpretation of results. 

Introduction. 

Iodate, detection of. 

Iodide. See iodine. 

reduction of antimonic salt. 

Iodine, free and combined detection of. 

properties of.. 

Iodic acid, properties of. 

tabulated tests of. 

Ionization, repression of. 

Ions and ionization. 

Iridium, compounds of. 

detection and properties of. 

solution of iridium alloys. 

Iron, compounds of. 

detection of. 

properties of. 

reaction with ferrous and ferric salts. 


PAG 

298-30 
303, 30 


... 5 

. .46, 6 
...25 

...12 
...27 
165,17 
...15 
...15 
... 25 
...18 

...21 
...32 
...15 
...15 
... 25 
...25 
...26 
...18 
...18 
... 4 


16 

22 j 
11 
2C 
22 \ 

23 


. 17! 

. £ 

_174,17 

_173, 27 

. 27 

. 21 

. 1 

.3, 

. 27 

. 2 £ 

. 2 £ 

. 27 

86 , 100, 24 

. 8 

. £ 























































INDEX 


341 


PAGE 

on, separations. 109 

table of reactions with. 246 

test for cyanide. 179 

ferrioyanide. 180 

ferrocyanide. 179 

thiocyanate. 180 

iboratory directions. 16 

exercises. See group in question. 

ictic acid. 277 

table of reactions.*. 261 

mthanum oxalate. 277 

3ad acetate, reactions with acids.254-261 

test for aluminum. 84 

chromate.84,195 

phosphate. 196 

sulphate. 197 

sulphide. 167 

sad, compounds of. 277 

detection of.34,37,240 

oxide test for manganese. 56 

properties of.! 33 

reactions with reagents. L . 37, 56, 240 

tabulated tests of. 240 

ess common elements. Part VI. 293 

ime water test for ammonia. 143 

C0 2 .158,164 

magnesium. 142 

iquid, preliminary examination of. 221 

ithium, compounds of. 278 

detection of.252, 323 

properties of. ... .. 322 

tables of tests. 252 

itmus test for ammonia..•. 143 

oop tube test. 164 

lagnesia mixture, reagent. 330 

test for arsenic. 69 

phosphate. 196 

lagnesium, compounds of.142, 278 

detection of.142, 250 

properties of. 142 

reactions with.146, 250 

separations. 150 

lalic acid, table of tests for. 261 

langanese, compounds of... 279 

detection of, soils, minerals, etc. 88 

properties of... 87 

reactions with reagents...103, 248 

separations. 109 




















































342 


INDEX 


Manganese, tables of reactions with.. 

Marsh test for antimony and arsenic. 

Mass action, law of. 

Mendeleef’s Periodio table of elements. 

Mercuric chloride, reaction with As, Sb, Sn. 

test for iodine. 

mercury, reactions with. 

Mercurous chloride, detection of. 

mercury, reactions with. 

nitrate, test for chromium. 

Mercury, compounds of. 

detection of -us-monovalent. 

-ic-divalent. 

properties of. 

metallic, recognition of. 

reactions with reagents. 

Metallio, displacement of platinum. 

precipitations. See Table of Reactions. 

Metals, general grouping of. 

systematic analysis of. 

Metaphosphoric acid, detection. 

properties of. 

reactions. 

Metasilioate. See silicic acid. 

Metastannic acid. 

Microcosmic salt test for silicate. 

Minerals, detection of antimony in. 

gold in. 

Miscellaneous tests of metals. See Part V. 
Molybdenum, property, solubility, tests of. 


PAG 

. 24 

. 50,5 

. 1 

. 32 

..244,24. 

. 17 

.. 5 

. 3 

. 3 

. e 

. 28 , 

. 3 

. 6 

. 3 

. 

37, 56, 240, 24 


26, 2 
• 22 
. 19 
. 19 
. 25 

• *0 

. 16 

. 5 
. 29 

• 30 


Nessler’s reagent. 

test for ammonia. 

Neutral, neutralization, definitions of. 

Nickel, compounds of. 

detection of. 

properties of. 

reactions with reagents. 

separations. 

tables of tests of. 

Nitrate, detection of. 

Nitric acid, detection of. 

properties of. 

solution of substances... . 

tabulated tests of. 

test of salicylate. 

Nitrite, detection of. 

in water. 

distinction from chlorite.... 
test for iodide. 


33 


. II 

. 28 

89, 106, 24 

. ej 

:::::::: 

. 24 

.201, 20 

.201, 2C 

. 20 

.22 

. 25 

. 20 

. 16 

. 16 

.158, 15 

. 17 


















































INDEX 


343 


'itrogen, compounds of. 

detection of. 

properties of. 

solubility in water. 

itroso B naphthol test for cobalt. 

itrous acid, properties and detection. 

open-tube test for arsenic. 

I tabulated tests of. 

otes. See throughout text. 

rganic acids, detection of. 

group.'. 

list of. 

separations. 

rthophosphoric acid, properties and detection, 
rthosilicate. See silicic acid. 

S'smium, compounds of. 

detection. 

properties of. 

•smotic pressure. 

Oxalic acid, detection of. 

properties. 

test for calcium. 

platinum.. 

Oxidation, definition of. 

of ferrous iron... 

test for chromate. 

without blowpipe. 

)xidizing action of chlorate. 

( agent, action on sulphide. 

flame. 

)xygen, solubility in water. 

Palladium, compounds of. 

properties and tests of. 

Perchlorate, detection of. 

Perchloric acid.. 

Permanganate, permanganic acid, detection of 

properties of. 

test for nitrite. 

Persulphate method for separation of halogens. 

Phenolsulphonic acid reagent. 

test for nitrate. 

Iphenylhydrazine acetate test for gold. 

IPhosphate. See phosphoric acid. 

Phosphoric acid, properties and detection. 

removal from solution. 

tables of reactions. 

Phosphorous acid, properties and detection of 
tables of reactions. 


PAGE 
. 282 
. 201 
. 200 
4 

. 103 
. 159 
. 52 
. 258 


... 210 
.... 207 
... 156 
... 210 
190, 196 

.... 282 
.... 300 
.... 299 
. . . . 5 

115. 209 
208, 283 
.... 127 
.... 296 
. . . . 3 

.... 99 

. . .. 97 

.... 18 
.... 203 
.... 167 
.... 17 

. . . . 4 

.283, 300 
.... 299 
.172,200 
.... 283 
.202,205 
.202,283 
.... 165 
.... 182 
.... 330 

. 204 

. 295 

.189,196 

. 115 

. 258 

.... 190 
. 258 


















































344 


INDEX 


Phosphorus and its acids, descriptive. 

compounds of. 

detection of element. 

Physical examination of solids. 

Platinic acid test for ammonia. 

potassium. 

Platinum, compounds of. 

detection and properties of. 

metal group. 

separation from H 2 S group. 

table of reactions with. 

Potassium chloride test for platinum.. 

chromate reactions with Ag, Hg, Pb. 

Ba. 

Bi, Cd, Cu, Hg. 

See HC1 and H 2 S group laboratory exercises. 

compounds of. 

cyanide reactions with Bi, Cd, Cu, Hg + +. 

detection and properties. 

dichromate test for iodide.. 

ferricyanide test for ferrous iron.. 

tests for Cr, Fe. 

Co, Ni, Mn, Zn. 

See also exercises under metals. 

test for copper. 

ferric iron. 

zinc. 

tests for Ag, Hg+, Pb. 

Bi, Cd, Cu, Hg+ +. 

Al, Fe. 

Co, Ni, Mn, Zn. 

See also exercises on metals mentioned. 

iodide test for nitrite. 

platinum. 

nitrite test for cobalt. 

permanganate test for nitrite. 

reactions with reagents. 

sulphocyanate test for cobalt. 

table of reactions. 

Potential series. 

Precipitation, definition of. 

laws governing. 

test for fluoride. 

Pressure, effect on solubilities. 

Prussian blue, test for cyanide.. 

Pseudo solution, definition of. 

Pyroantimonate test for sodium. 

Pyrophosphorio acid, property and detection. 

table of reactions with.. 


PAGB 

. 18€' 

. 28a' 

. . ..189, 19C 

. 211 

. 147 

. 147 

.283 

. 295 

. 298* 

. 75 

. 245 

. 297 

.240 

. 250 

. 242 

. 283 

.242 

. 144 

...... 178 

.87,89 

. 246 

. 249 

. 48 

87, 89, 100 

. 91 

. 241 

. 242 

. 247 ' 

. 249 

. 165 

. 297 

. ...85,103 

. 159 

. 147 

. 85 

. 252 

. 14 

. 1 

. 13 

. 195 

. 4 

. 179 

. 3 

...145,148 

. 190 

.258 

















































INDEX 


345 


ialitative analysis, definition of. 

lantitative analysis, definition of. 

lestions, reviews of sections. See at close of each group. 

I 

ire earths, cerium and. 

detection of. 

properties of. 

separations of. 

irer elements of the alkali group. 

ammonium sulphide group. 

hydrogen sulphide group. 

saction, definition of. 

law for complete. 

limits, studies in. 

eactions—acid groups. 

barium chloride group. 

organic acid group. 

silver nitrate group. 

soluble acid group. 

tables of.<r • 

volatile acid group. 

metal groups. 

ammonium carbonate group. 

sulphide group. 

hydrogen chloride group. 

sulphide group. 

soluble metal group. 

rarer elements. 

tables of. 

Reagents, care of. 

definition of. 

list of—acid solutions. 

compounds. 

solids. 

quantity to be used. 

special, preparation of. 

tecording results, suggestion regarding. 

ieducing agents, action on chlorate. 

test for bismuth. 

chromium. 

molybdenum. 

vanadium. 

flame. 

deduction, definition of. 

of ferric salts. 

test for chromate. 

sulphate. 

tin. 

zinc.. 

See also reducing agents. 


PAGB 

1 

1 


.310 

. 313 

. 310 

. 312 

_322-324 

_310-322 

_293-309 

. 2 

. 10 

. 210 

_192-179 

_209, 210 

_176-180 

_203-206 

_254-261 

_164-168 

_129-133 

.92-108 

..37-39 

56-59, 68-73 

_146-148 

.293-323 

.240-253 

. 32 

. 1 

. 326 

. 327 

. 32 

. 32 

. 329 

. 23 

. 203 

. 46 

.97,194 

. 304 

. 319 

. 16 

. 3 

. 101 

. 97 

. 197 

. 55 

.. 90 

















































346 


INDEX 


Reduction, test for without the blowpipe. 

Reinsch’s test for arsenic. 

Residue, definition of. 

Reversible reaction. 

Rhodium, compounds of. 

detection of. 

solution of alloys of. 

Rubidium, detection of. 

Ruthinium, compounds. 

detection and properties. 

solution of alloys of. 


PAG 

] 


28 

3C 

3C 

32 

28 

30 

30 


Salicylic acid, salicylate, detection of. 

properties of. 

tabulated tests of. 

test for iron. 

Scott’s hydrogen sulphide generator. 

Selenium, compounds of. 

detection of. 

properties of. 

solubility of. 

Separation of the acids —See group in question of the alkali metals 

alkaline earth metals. 

ammonium carbonate group. 

sulphide group. 

hydrogen chloride group. 

sulphide.. 

soluble group metals. 

metal groups. 

Silicate tests for. 

Silicic acid, detection of. 

properties of. 

tabulated tests. 

Silicon, compounds. . 

See silicic acid. 

Silver chloride, distinction from mercurous chloride. 

properties of. 

coin test for sulphide. 

compounds of. 

detection and properties of. 

nitrate group. 

descriptive. 

reaction of members. 

Silver nitrate reactions with acids. 

As, Sb, Sn. 

table of analysis. 

test for arsenate. 

bromide. 

chloride. 

chromate. 


. 20 

.20 

. 26 

.8 

. 6 

. 28 

.30 

. 30 

. 30 

.149-15 

.134-13: 

.134-13) 

.109-12! 

.40-4) 

. .. 60-63, 74-7! 

.149-15: 

.28-31, 230, 23: 

. 16( 

. 161 

. 16( 

. ... 256 

. 28 1 

. 36 

. 36 

. 167 

. 285 

.35-36 

. 155 

. 17C 

. 176 

.254-261 

.244, 245 

. 181 

. 193 

.173, j.77 

.171,176 

. 195 


















































INDEX 


347 


PAGE 


Silver nitrate test for cyanide. r . 178 

ferricyanide. 180 

ferrocyanide. 179 

iodide. 177 

nitrite. 166 

phosphate. 196 

tartrate. 210 

thiocyanate. 180 

tin. 55 

Silver, reactions with. 38 

tabulated tests with. 240 

thiocyanate. 38 

Sodium bismuthate test for manganese. 88 

carbonate, reactions with Ag, Hg, Pb. 241 

Bi, Cd, Cu, Hg+ +. 243 

cobaltic nitrate reagent. 330 

compounds of. 287 

hydroxide reactions with Ag, Hg, Pb. 241 

Bi, Cd, Cu, Hg++. 243 

Al, Cr, Fe. 247 

Co Ni, Mn, Zn. 249 

Ba, Ca, Sr, Mg. 250 

NHa. 252 

test for platinum. 297 

phosphate reactions with Al, Cr, Fe. 247 

Co, Ni, Mn, Zn. 248 

Ba, Ca, Sr, Mg. 250 

Li. 252 

properties and detection. 145 

reactions with reagents. 148 

tabulated tests of. 252 

thiosulphate test for molybdenum. 304 

Solid, preliminary examination of. 211 

Solubility of elements—-See element in question. 

product. 12 

table. 262 

Soluble acid group. 156 

basic group.. • • 140 

H 2 S group, separation from insoluble H 2 S group. 61 

H 2 S sub-group B.49, 74-79 

reactions of members. 68 

metal group. See also alkali group. 

Solution, preparation of.222, 228, 233 

of alloys.226—228 

substances for acid analysis. 233 

metal analysis. 222 

See solubilities under properties of elements. 

laws governing. 13 

theory of. 4 

Spectrum tests of alkaline earths. 127 




















































348 


INDEX 


Spectrum tests of alkalies.. 

Splashing, prevention of. 

Stannic acid... 

Stannite test for bismuth. 

Stannous chloride, preparation of. 

reactions with Ag, Hg + , Pb. 

Bi, Cd, Cu, Hg+ + .. 

test for platinum.. • • 

Starch paste, preservation of. 

Stoppers, notes regarding. 

Strontium, compounds of. 

detection of. 

properties of. 

reactions with reagents. 

sulphate test for barium. 

Suction, directions for filtration. 

Suggestions for laboratory practice. 

Sulphate method for separating halogens. 

properties and detection. See sulphuric acid. 

separation trom sulphite. 

test for barium. 

test for strontium. 

Sulphide, detection and reactions. 

Sulphite properties and detection. 

Sulphocyanate test for cobalt. 

» iron... 

Sulphocyanic acid, properties and detection. 

Sulphur, compounds of. 

dioxide, detection of. 

occurrence and properties. 

solubility in water. 

test for molybdenum. 

Sulphuric acid, detection and properties. 

free, detection of. 

reactions with Ag, Hg, Pb. 

tabulated tests for. 

test for acetate. 

acids, table of. 

chlorate. 

tartrate. .. 

Sulphurous acid, properties and detection. 

tabulated tests for. 

Systematic analysis of substances. 


PAGE 

... 144 
... 32 

... 72 

... 46 

... 330 
... 241 
... 243 
... 297 
... 330 
... 32 

... 287 
... 127 
... 127 
132, 250 
... 126 
... 21 
... 24 

... 182 

... 169 
... 126 
.... 128 
... 167 
163, 168 
... 85 

... 87 

175,259 
,... 289 
163, 168 
161, 162 
... 4 

... 304 
191, 197 
... 191 
.... 241 
,... 259 
, ... 209 
... 22C 
.... 203 
.... 209 
163, 168 
.... 259 
.... 213 


Tables of reactions, acids. 254 

metals. 24( 

separation of metals. 23( 

use of, directions for. 31 

Tannic acid, tests for. 26. 

Tantalum, compounds of. 281 


















































INDEX 


349 


PAGE 

artario acid, detection of...209, 261 

properties of. 208^ 

'ellurium, compounds of. 289 

detection of. 306 

property, solubility. 305 

'emperature, effect on solubility. 4 

'erms, definitions of chemical. 1 

’est tube. 20 

brush. 23 

rack. 23 

'hallium, compounds of..... 289 

'heory of solution. 4 

'hiocyanate test for iron. 101 

silver. 36 

'hiocyanic acid, detection of. 180 

properties of.-. 175 

'hiosulphate, detection of.163, 168 

properties of. 163 

test for aluminum. 82 

'hiosulphuric acid, reactions. 259 

I'horium, compounds of. 289 

detection of. 316 

■ properties and solution. 315 

'in, compounds of. 288 

detection of. 54 

group. 49 

I properties of. 54 

reactions with. 71 

separation. 74 

table of reactions with. 245 

'itanium, compounds of. 290 

detection and properties...,• • • • 316 

’races. See element in question. 

I'ungsten, compounds of. 290 

detection of. 308 

properties and solution. 307 

’urmeric test for borate. 185 


Jranium, compounds of. 

detection of. 

properties and solution. 


Vanadium, compounds of. 

detection. . 

properties and solutson. 

j/erdigris. See Copper. 

/olatile acid group. 

summary oft •••• t • t ••• f t 

iWall saltpeter. See nitrio acid. 


... 291 
... 319 
318,319 
... 48 

155, 157 
.169 


















































350 


INDEX 


Wash bottle... 

Washing precipitates, definition. 

Wet methods for copper tests. . ..., 

silver tests. 

Work, preparation for laboratory. 


PAGE 
. 20 
2 

. 48 
. 36 
. 32 


Zinc, compounds of. 

detection of. 

reactions with. 

separation from group. 

tables of reactions with. 

Zirconium, compounds of. 

detection of. 

properties and solution of 


... 291 
... 90 

... 107 
109-123 
... 248 
... 291 
... 322 
... 321 




































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o£ 1 ‘orazi.soiqduro ui asmo3 }ioi{<s- 

Caven, R. M., and Lander, G. D. Systematic Inorganic Chem¬ 
istry . i2mo, *2 00 

Chalkley, A. P. Diesel Engines.8vo, 

Chalmers, T. W. The Production and Treatment of Veg¬ 
etable Oils.4to, 

Chambers’ Mathematical Tables. 8vo, 

Chambers, G. F. Astronomy.i6mo, 

Chappel, E. Five Figure Mathematical Tables.8vo, * 

Charnock. Mechanical Technology. 8vo, * 

Charpentier, P. Timber.8vo, 

Chatley, H. Principles and Designs of Aeroplanes. (Science 

Series.) .i6mo, 

-How to Use Water Power.i2mo, 

-Gyrostatic Balancing. 8vo, 


4 00 

7 50 
1 75 
1 50 


3 00 
*6 00 


o 50 































10 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Child, C. D. Electric Arcs. 8v0 > 2 00 

Christian, M. Disinfection and Disinfectants. Trans, by 

Chas. Salter .12010, 2 00 

Christie, W. W. Boiler-waters, Scale, Corrosion, Foaming, 

8vo, *3 00 

-Chimney Design and Theory.8vo, *3 00 

-Furnace Draft. (Science Series, No. 123).i6mo, o 50 

_Water, Its Purification and Use in the Industries-8vo, *2 00 

Church’s Laboratory Guide. Rewritten by Edward Kinch.Svo, *1 50 

Clapham, J. H. Woolen and Worsted Industries.8vo, 2 00 

Clapperton, G. Practical Papermaking.8vo, 2 50 

Clark, A. G. Motor Car Engineering. 

Vol. I. Construction. *3 00 

Vol.II. Design. (In Press.) 

Clark, C. H. Marine Gas Engines. New Edition. (In Press.) 

Clark, J. M. New System of Laying Out Railway Turnouts, 

i2mo, 1 00 

Clarke, J. W., and Scott, W. Plumbing Practice. 

Vol. I. Lead Working and Plumbers’ Materials. .8vo, *4 00 

Vol. II. Sanitary Plumbing and Fittings. (In Press.) 

Vol. III. Practical Lead Working on Roofs....*- (In Press.) 

Clarkson, R. B. Elementary Electrical Engineering. 

(In Press.) 

Clausen-Thue, W. ABC Universal Commercial Telegraphic 


Code. Sixth Edition. (In Press.) 

Clerk, D., and Idell, F. E. Theory of the Gas Engine. 

(Science Series No. 62.).i6mo, o 50 

Clevenger, S. R. Treatise on the Method of Government 

Surveying .i6mo, mor., 2 50 

Clouth, F. Rubber, Gutta-Percha, and Balata.8vo, *5 00 


Cochran, J. Treatise on Cement Specifications.8vo, *1 00 

-Concrete and Reinforced Concrete Specifications... .8vo, *2 50 

Cochran, J. Inspection of Concrete Construction.8vo, *4 00 

Cocking, W. C. Calculations for Steel-Frame Structures. 12m0, 2 25 

Coffin, J. H. C. Navigation and Nautical Astronomy.. i2mo, *3 50 
Colburn, Z., and Thurston, R. H. Steam Boiler Explosions. 

(Science Series No. 2.).i6mo, o 50 




















D. VAN NOSTRAND COMPANY S SHORT-TITLE CATALOG II 


Cole, R. S. Treatise on Photographic Optics.i2mo, 

Coles-Finch, W. Water, Its Origin and Use.8vo, 

Collins, C. D. Drafting Room Methods, Standards and 

Forms.8vo, 

Collins, J. E. Useful Alloys and Memoranda for Goldsmiths, 

Jewelers.i6mo, 

Collis, A. G. High and Low Tension Switch-Gear Design.8vo, 

-Switchgear. (Installation Manuals Series.).i2mo, 

Comstock, D. F., and Troland, L. T. The Nature of Matter 

and Electricity.i2mo, 

Coombs, H. A. Gear Teeth. (Science Series No. 120).. .i6mo, 

Cooper, W. R. Primary Batteries.8vo, 

Copperthwaite, W. C. Tunnel Shields.4to, 

Corfield, W. H. Dwelling Houses. (Science Series No. 50.) i6mo, 

-Water and Water-Supply. (Science Series No. 17.).. i6mo, 

Cornwall, H. B. Manual of Blow-pipe Analysis.8vo, 

Cowee, G. A. Practical Safety Methods and Devices... .8vo, 

Cowell, W. B. Pure Air, Ozone, and Water.nmo, 

Craig, J. W., and Woodward, W. P. Questions and Answers 

about Electrical Apparatus.i2mo, leather, 

Craig, T. Motion of a Solid in a Fuel. (Science Series No. 49.) 

i6mo, 

-Wave and Vortex Motion. (Science Series No. 43.). i6mo, 

Cramp, W. Continuous Current Machine Design.8vo, 

Creedy, F. Single-Phase Commutator Motors.8vo, 

Crehore, A. C. Mystery of Matter and Energy.i2mo, 

Crocker, F. B. Electric Lighting. Two Volumes. 8vo. 

Vol. I. The Generating Plant. 

Vol. II. Distributing Systems and Lamps. 

Crocker, F B., and Arendt, M. Electric Motors.8vo, 

-and Wheeler, S. S. The Management of Electrical Ma¬ 
chinery.i2mo, 

Cross, C. F., Bevan, E. J., and Sindall, R. W. Wood Pulp and 

Its Applications. (Westminster Series.).. .8vo, 

Crosskey, L. R. Elementary Perspective.8vo, 

Crosskey, L. R., and Thaw, J. Advanced Perspective.8vo, 

Culley, J. L. Theory of Arches. (Science Series No. 87.). i6mp, 
Cushing, H. C., Jr., and Harrison, N. Central Station Man¬ 
agement . 

Dadourian, H. M. Analytical Mechanics.8vo. 


1 50 
5 00 

2 00 

o 50 
k 3 5 o 
o 50 

2 00 
o 50 
: 4 00 
! g 00 
o 50 
o 50 

! 2 50 
^3 00 
■2 00 

I 50 

0 50 

O 50 
^2 50 
k 2 00 
I 00 

3 00 

*2 50 

*1 00 

*2 00 
I 25 

I 50 

o 50 

*2 OO 

*3 00 


























12 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Dana, R. T. Handbook of Construction Plant..i2mo, leather, *5 00 

-Handbook of Construction Efficiency. (In Press.) 

Danby, A. Natural Rock Asphalts and Bitumens.8vo, *2 50 

Davenport, C. The Book. (Westminster Series.).8vo, *2 00 

Davey, N. The Gas Turbine.8vo, *4 00 

Davies, F. H. Electric Power and Traction.8vo, *2 00 

-Foundations and Machinery Fixing. (Installation Manuals 

Series) .i6mo, *1 00 

Deerr, N. Sugar Cane. .8vo, 8 00 

Deite, C. Manual of Soapmaking. Trans, by S. T. King. -4to, *5 00 

De la Coux, H. The Industrial Uses of Water. Trans, by A. 

Morris.8vo, *4 50 

Del Mar, W. A. Electric Power Conductors.8vo, *2 00 

Denny, G. A. Deep-Level Mines of the Rand.4to, *10 00 

-Diamond Drilling for Gold. *5 00 

De Roos, J. D. C. Linkages. (Science Series No. 47.)... i6mo, o 50 


Derr, W. L. Block Signal Operation.Oblong nmo, *1 50 

-Maintenance of Way Engineering. (In Preparation.) 


Desaint, A. Three Hundred Shades and How to Mix Them. 

8vo, 8 00 

De Varona, A. Sewer Gases. (Science Series No. 55.)... i6mo, o 50 
Devey, R. G. Mill and Factory Wiring. (Installation Manuals 

Series.).i2mo, *1 00 

Dibdin, W. J. Purification of Sewage and Water.8vo, 6 50 

Dichman, C. Basic Open-Hearth Steel Process.8vo, *3 50 

Dieterich, K. Analysis of Resins, Balsams, and Gum Resins 

8vo, *3 00 

Dilworth, E. C. Steel Railway Bridges.4to, *4 00 

Dinger, Lieut. H. C. Care and Operation of Naval Machinery 

i2mo. 

Dixon, D. B. Machinist’s and Steam Engineer’s Practical Cal¬ 
culator.i6mo, mor., 1 25 

Dodge, G. F. Diagrams for Designing Reinforced Concrete 

Structures .folio, *4 00 

Dommett, W. E. Motor Car Mechanism.i2mo, *i 50 

Dor^ B. F. The Surveyor’s Guide and Pocket Table-book. 

i6mo, mor., 2 00 























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 13 


Draper, C. H. Elementary Text-book of Light, Heat and 

Sound.-.i2mo, i oo 

Draper, C. H. Heat and the Principles of Thermo-dynamics, 

i2mo, 2 oo 

Dron, R. W. Mining Formulas.i2mo, i oo 

Dubbel, H. High Power Gas Engines.8vo, *5 00 

Dumesny, P., and Noyer, J. Wood Products, Distillates, and 

Extracts.8vo, *4 50 

Duncan, W. G., and Penman, D. The Electrical Equipment of 

Collieries.8vo, *4 00 

Dunkley, W. G. Design of Machine Elements. 2 vols. 

i2mo, each, *1 50 

Dunstan, A. E. f and Thole, F. B. T. Textbook of Practical 

Chemistry.i2mo, *1 40 

Durham, H. W. Saws.8vo, 2 50 

Duthie, A. L. Decorative Glass Processes. (Westminster 

Series).8vo, *2 00 

Dwight, H. B. Transmission Line Formulas.8vo *2 00 

Dyson, S. S. Practical Testing of Raw Materials.8vo, *5 00 

-and Clarkson, S. S. Chemical Works.8vo, *7 50 


Eccles, W. H. Wireless Telegraphy and Telephony.. i2mo, *4 50 
Eck, J. Light, Radiation and Illumination. Trans, by Paul 

Hogner. 8vo, 

Eddy, H. T. Maximum Stresses under Concentrated Loads, 

8vo, 

Eddy, L. C. Laboratory Manual of Alternating Currents, 

i2mo, 

Edelman, P. Inventions and Patents.i2mo 

Edgcumbe, K. Industrial Electrical Measuring Instruments. 

8vo, (In Press.) 

Edler, R. Switches and Switchgear. Trans. \)y Ph. Laubach. 

8vo, 

Eissler, M. The Metallurgy of Gold.8vo, 

-The Metallurgy of Silver.8vo, 

-The Metallurgy of Argentiferous Lead.8vo, 

-A Handbook of Modern Explosives.8vo, 

Ekin, T. C. Water Pipe and Sewage - Discharge Diagrams 

folio, *3 00 


*2 50 

1 50 

o 50 
*1 50 


*4 00 
7 50 

4 00 

5 00 
5 00 






















14 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Electric Light Carbons, Manufacture of.8vo, i oo 

Eliot, C. W., and Storer, F. H. Compendious Manual of Qualita¬ 
tive Chemical Analysis.i2mo, *i 25 

Ellis, C. Hydrogenation of Oils.8vo, (In Press.) 

Ellis, G. Modern Technical Drawing.8vo, *2 00 

Ennis, Wm.D. Linseed Oil and Other Seed Oils .8vo, *4 00 

-Applied Thermodynamics.8vo, *4 50 

-Flying Machines To-day.i2mo, *1 50 

-Vapors for Heat Engines.i2mo, *1 00 

Ermen, W. F. A. Materials Used in Sizing.8vo, *2 00 

Erwin, M. The Universe and the Atom.i2mo, *2 00 

Evans, C. A. Macadamized.Roads. (In Press.) 

Ewing, A. J. Magnetic Induction in Iron.8vo, *4 00 


Fairie, J. Notes on Lead Ores. i2mo, *0 50 

—— Notes on Pottery Clays.i2mo, *1 50 

Fairley, W., and Andre, Geo. J. Ventilation of Coal Mines. 

(Science Series No. 58.).i6mo, 0 50 

Fairweather, W. C. Foreign and Colonial Patent Laws .. .8vo, *3 00 

Falk, M. S. Cement Mortars «nd Concretes.8vo, *2 50 

Fanning, J. T. Hydraulic and Water-supply Engineering.8vo, *5 00 

Fay, I. W. The Coal-tar Colors.8vo, *4 00 

Fernbach, R. L. Glue and Gelatine..8vo, *3 00 

Findlay, A. The Treasures of Coal Tar. . .i2mo, 2 00 

Firth, J. B. Practical Physical Chemistry.i2mo, *1 25 

Fischer, E. The Preparation of Organic Compounds. Trans. 

by R. V. Stanford.i2mo, *1 25 

Fish, J. C. L. Lettering of Working Drawings. .. .Oblong 8vo, 1 00 

-Mathematics of the Paper Location of a Railroad, 

i2mo, paper, *0 25 

Fisher, H. K. C., and Darby, W. C. Submarine Cable Testing. 

8vo, *3 50 

Fleischmann, W. The Book of the Dairy. Trans, by C. M. 


Aikman.8vo, 4 00 

Fleming, J. A. The Alternate-current Transformer. Two 

Volumes.8vo, 

Vol. I. The Induction of Electric Currents. *5 5° 

Vol. II. The Utilization of Induced Currents. *5 50 




























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 15 


Fleming, J. A. Propagation of Electric Currents.8vo, *3 00 

-A Handbook for the Electrical Laboratory and Testing 

Room. Two Volumes.8vo, each, *5 00 

Fleury, P. Preparation and Uses of White Zinc Paints..8vo, *2 50 
Flynn, P. J. Flow of Watc-r. (Science Series No. 84.).i2mo, o 50 

-Hydraulic Tables. (Science Series No. 66.).i6mo, o 50 

Forgie, J. Shield Tunneling..8vo. {In Press.) 

Foster, H. A. Electrical Engineers’ Pocket-book. (Seventh 

Edition.) .i2mo, leather, 5 00 , 

-. Engineering Valuation of Public Utilities and Factories, 

8vo, *3 00 

-Handbook of Electrical Cost Data.8vo. {In Press) 

Fowle, F. F. Overhead Transmission Line Crossings-i2mo, *1 50 

-The Solution of Alternating Current Problems.8vo {In Press.) 

Fox, W. G. Transition Curves. (Science Series No. no.).i6mo, o 50 
Fox, W., and Thomas, C- W. Practical Course in Mechanical 

Drawing.i2mo, 1 25 

Foye, J. C. Chemical Problems. (Science Series No. 69.).i6mo, 0 50 

-Handbook of Mineralogy. (Science Series No. 86.). 

i6mo, o 50 

Francis, J. B. Lowell Hydraulic Experiments.4to, 15 00 

Franzen, H. Exercises in Gas Analysis.nmo, *1 00 

Freudemacher, P. W. Electrical Mining Installations. (In¬ 
stallation Manuals Series.). i2mo, *1 00 

Friend, J. N. The Chemistry of Linseed Oil..i2mo, 1 00 

Frith, J. Alternating Current Design. 8vo > *200 

Fritsch, J. Manufacture of Chemical Manures. Trans, by 

D. Grant.. ■ •* vo > *4 00 

Frye, A. I. Civil Engineers’ Pocket-book.i2mo, leather, 5 00 

Fuller, G. W. Investigations into the Purification of the Ohio 

t,. .ato, *10 00 

River... J ’ * 

Furnell, J. Paints, Colors, Oils, and Varnishes. 8v0 > 1 00 

Gairdner. J. W. I. Earthwork.. (/n Press.) 

Gant, L. W. Elements of Electric Traction.° v0 ' 2 50 

Garcia, A. J. R. V. Spanish-English 4 50 

Gardner, H. A. Paint Researches and Their tactical 

Application . ’ 
























16 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Garforth, W. E. Rules for Recovering Coal Mines after Explo¬ 
sions and Fires.12mo, leather, i 50 

Garrard, C. C. Electric Switch and Controlling Gear....8vo, *6 00 

Gaudard, J. Foundations. (Science Series No. 34.).i6mo, o 50 

Gear, H. B., and Williams, P. F. Electric Central Station Dis¬ 
tributing Systems.8vo, 3 00 

Geerligs, H. C. P. Cane Sugar and Its Manufacture.8vo, *500 

-Chemical Control in Cane Sugar Factories.4to, 4 00 

Geikie, J. Structural and Field Geology.8vo, *4 00 

-Mountains, Their Origin, Growth and Decay.8vo, *4 00 

- The Antiquity of Man in Europe.8vo, *3 00 

Georgi, F., and Schubert, A. Sheet Metal Working. Trans 

by C. Salter.8vo, 3 00 

Gerhard, W. P. Sanitation, Water-supply and Sewage Dis¬ 
posal of Country Houses. I2 mo, *2 00 

-Gas Lighting. (Science Series No. hi.) .i6mo, o 50 

Gerhard, W. P. Household Wastes. (Science Series No. 97.) 

tt x^ i6mo, o 50 

-House Drainage. (Science Series No. 63.).i6mo 050 

-Sanitary Drainage of Buildings. (Science Series No. 93.) 

Gerhardi, C. W. H. Electricity Meters. ^vo, *6 00 

Geschwind, L. Manufacture of Alum and Sulphates. Trans. 

by C. Salter.. 0Q 

Gibbings, A. H. Oil Fuel Equipment for Locomotives... 8vo* *2 50 

Gibbs, W. E. Lighting by Acetylene. I2m o, *1 50 

Gibson, A. H. Hydraulics and Its Application.8vo,’ *500 

—— Water Hammer in Hydraulic Pipe Lines.i 2 mo *2 00 

Gibson, A. H., and Ritchie, E. G. Circular Arc Bow Girder.4to, *3 50 

GHbreth F. B. Motion Study. . * 2 00 

-Bricklaying System. . 00 

— Field System..i2mo, leather, *3 00 

Primer of Scientific Management.i2mo, *1 00 

Gillette, H. P. Handbook of Cost Data. I2 mo, leather, *5 00 

-Rock Excavation Methods and Cost.i 2 mo, leather, *5 00 

-Handbook of Earth Excavation. (In Press) 

-Handbook of Tunnels and Shafts, Cost and Methods 

of Construction.(/* PresSt) 

-Handbook of Road Construction, Methods and Cost. .(In Press.) 

























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 17 


Gillette, H. P., and Dana, R. T. Cost Keeping and Manage¬ 
ment Engineering .8vo, *3 50 

and Hill, C. S. Concrete Construction, Methods and 

^ ost .8vo, *5 00 

Gillmore, Gen. Q. A. Roads, Streets, and Pavements.. .nmo, 1 25 
Godfrey, E. Tables for Structural Engineers. .i6mo, leather, *2 50 

Golding, H. A The Theta-Phi Diagram.i2mo, *1 25 

Goldschmidt, R. Alternating Current Commutator Motor. 8vo, *3 00 
Goodchild, W. Precious Stones. (Westminster Series.) 8vo, *200 
Goodell, J. M. The Location, Construction and Maintenance 

of Roads. gvo, x 00 

Goodeve, T. M. Textbook on the Steam-engine.i2mo, 2 00 

Gore, G. Electrolytic Separation of Metals.8vo, *3 50 

Gould, E. S. Arithmetic of the Steam-engine.i2mo, 1 00 

-Calculus. (Science Series No. 112.).i6mo, 050 

-High Masonry Dams. (Science Series No. 22.). . . i6mo, o 50 

-Practical Hydrostatics and Hydrostatic Formulas. (Science 

Series No. 117.).i6mo, o 50 

Gratacap, L. P. A Popular Guide to Minerals.8vo, *3 00 

Gray, J. Electrical Influence Machines.i2mo, 200 


Gray, J. Marine Boiler Design. .i2mo, *1 25 

Greenhill, G. Dynamics of Mechanical Flight.8vo. *2 50 

Gregorius, R. Mineral Waxes. Trans, bv C. Salter. . . i2mo, *3 00 

Grierson, R. Modern Methods of Ventilation.8vo, 3 00 

Griffiths, A. B. A Treatise on Manures.i2mo, 3 00 

Griffiths, A. B. Dental Metallurgy.8vo, *3 50 

Gross, E. Hops. 8vo, *4 50 

Grossman, J. Ammonia and its Compounds.i2mo, *1 25 

Groth, L. A. Welding and Cutting Metals by Gases or Electric¬ 
ity. (Westminster Series.).8vo, *2 00 

Grover, F. Modern Gas and Oil Engines.8vo, *200 


Gruner, A. Power-loom Weaving.8vo, *3 00 

Grunsky, C. E. Topographic Stadia Surveying.. . .i2mo, 2 00 

Giildner, Hugo. Internal-Combustion Engines. Trans, by 

H. Diedrichs. 4 to, 15 00 


























18 D. VAN NOSTRAND COMPANY^ SPIORT-TITLE CATALOG 

Gunther) C. 0 . Integration. 8v0 > ** 2 5 

Gurden, R. L. Traverse Tables.folio, half mor., *7 5 ° 

Guy, A. E. Experiments on the Flexure of Beams.Bvo, *1 25 

Haenig, A. Emery and the Emery Industry.8vo, *2 50 

Hainbach, R. Pottery Decoration. Trans, by C. Salter. i2mo, *300 

Hale, W. J. Calculations of General Chemistry.i2mo, *1 25 

Hall, C. H. Chemistry of Paints and Paint Vehicles-i2mo, *200 

Hall, G. L. Elementary Theory of Alternate Current Work¬ 
ing .Svo, *1 50 

Hall, R. H. Governors and Governing Mechanism.nmo, *2 00 

Hall, W. S. Elements of the Differential and Integral Calculus 

8vo, *2 25 

-Descriptive Geometry.8vo volume and 4to atlas, *3 5 ° 

Haller, G. F., and Cunningham, E.T. The Tesla Coil.i2mo, *123 

Halsey, F. A Slide Valve Gears..i2mo, 1 50 

-The Use of the Slide Rule. (Science Series No. 114.) 

i6mo, o 50 

-Worm and Spiral Gearing. (Science Series No. 116.) 

i6mo, o 50 


Hancock, H. Textbook of Mechanics and Hydrostatics.. . 8vo, 1 50 

Hancock, W. C. Refractory Materials. (Metallurgy Series .(In Press.) 

Hardy, E. Elementary Principles of Graphic Statics.i2mo, *1 50 

Haring, H. Engineering Law. 

Vol. I. Law of Contract.8vo, *4 00 

Harper, J. H. Hydraulic Tables on the Flow of Water.i6mo, *2 00 

Harris, S. M. Practical Topographical Surveying. (In Press.) 

Harrison, W. B. The Mechanics’ Tool-book.i2mo, 1 50 

Hart, J. W. External Plumbing Work.8vo, *3 00 

-Hints to Plumbers on Joint Wiping.8vo, *3 00 

-Principles of Hot Water Supply.8vo, *3 00 

-Sanitary Plumbing and Drainage.8vo, *3 00 

Haskins, C. H. The Galvanometer and Its Uses.i6mo, 1 50 

Hatt, J. A. H. The Colorist.square i2mo, *1 50 

Hausbrand, E. Drying by Means of Air and Steam. Trans. 

by A. C. Wright.i2mo, *2 00 

-Evaporating, Condensing and Cooling Apparatus. Trans. 

by A. C. Wright.8vo, *5 00 





























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 19 


Hausmann, E. Telegraph Engineering.8vo, 

Hausner, A. Manufacture of Preserved Foods and Sweetmeats. 

Trans, by A. Morris and H. Robson..8vo, 

Hawkesworth, T. Graphical Handbook for Reinforced Concrete 

Design.. . . 4 to, 

Hay, A. Continuous Current Engineering.8vo, 

Hayes, H. V. Public Utilities, Their Cost New and Deprecia¬ 
tion.8 vo, 

-Public Utilities, Their Fair Present Value and Return, 

8vo, 

Heath, F. H. Chemistry of Photography.8vo {In 

Heather, H. J. S. Electrical Engineering.8vo, 

Heaviside, 0 . Electromagnetic Theory. 

Vols. I and II.8vo, each, 

Vol. Ill.8vo, 

Heck, R. C. H. Steam Engine and Turbine.8vo, 

-Steam-Engine and Other Steam Motors. Two Volumes. 

Vol. I. Thermodynamics and the Mechanics.8vo, 

Vol. II. Form, Construction and Working.8vo, 

-Notes on Elementary Kinematics.8vo, boards, 

-Graphics of Machine Forces..8vo, boards, 

Heermann, P. Dyers’ Materials. Trans, by A. C. Wright. 


i2mo, 

Heidenreich, E. L. Engineers’ Pocketbook of Reinforced 

Concrete .i6mo, leather, 

Heliot, Macquer and D’Apligny. Art of Dyeing Wool, Silk and 


Cotton. 8vo, 

Henrici, 0 . Skeleton Structures.8vo, 


Hering, C., and Getmann, F. H. Standard Tables of Electro¬ 
chemical Equivalents. 

Hering, D. W. Essentials of Physics for College Students. 

8vo, 

Hering-Shaw, A. Domestic Sanitation and Plumbing. Two 


Vols.8vo, 

-Elementary Science.8vo, 

Herington, C. F. Powdered Coal as a Fuel.8vo, 

Hermann, G. The Graphical Statics of Mechanism. Trans. 

by A. P. Smith.i2mo, 

Herzfeld, J Testing of Yarns and Textile Fabrics.8vo, 


*3 00 

*3 00 

*2 50 
*2 50 

*2 00 

*2 00 
Press.) 

*3 50 

*5 00 
*7 50 
*3 50 

*3 50 
*5 00 
*1 00 
*1 00 

*2 50 
*3 00 

*2 00 

1 50 

*2 00 

*1 75 

*5 00 
*2 00 

3 00 

2 00 
*3 50 


























20 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Hildebrandt, A. Airships, Past and Present..8vo, *3 50 

Hildenbrand, B. W. Cable-Making. (Science Series No. 32.) 

i6mo, o 50 

Hilditch, T. P. Concise History of Chemistry.i2mo, *1 25 

Hill, C. S. Concrete Inspection.i6mo, *1 00 

Hill, C. W. Laboratory Manual and Notes in Beginning 

Chemistry.(/ n Press.) 

Hill, J. W. The Purification of Public Water Supplies. New 

Edition.(7n Press.) 

- -Interpretation of Water Analysis. (In Press.) 

Hill, M. J. M. The Theory of Proportion.8vo, *2 50 

Hiroi, I. Plate Girder Construction. (Science Series No. 95.) 

i6mo, o 50 

-Statically-Indeterminate Stresses.i2mo, *2 00 

Hirshfeld, C. F. Engineering Thermodynamics. (Science 

Series No. 45).i6mo, o 50 

Hoar, A. The Submarine Torpedo Boat.i2mo, *2 00 

Hobart, H. M. Heavy Electrical Engineering....8vo, *4 50 

-Design of Static Transformers.i2mo, *2 00 

-Electricity.8vo, *2 00 

—-Electric Trains....8vo, *2 50 

-Electric Propulsion of Ships.8vo, *2 50 


Hobart, J. F. Hard Soldering, Soft Soldering, and Brazing. 

i2mo, *1 00 

Hobbs, W. R. P. The Arithmetic of Electrical Measurements 


i2mo, o 75 

Hoff, J. N. Paint and Varnish Facts and Formulas . i2mo, *150 

Hole, W. The Distribution of Gas.8vo, *7 50 

Holley, A. L. Railway Practice.folio, 6 00 

Hopkins, N. M. Model Engines and Small Boats.i2mo, 1 25 

Hopkinson, J., Shoolbred, J. N., and Day, R. E. Dynamic 

Electricity. (Science Series No. 71.).. i6mo, o 50 

Horner, J. Practical Ironfounding.8vo, *2 00 

-Gear Cutting, in Theory and Practice.8vo, *3 00 

Horniman, R. How to Make the Railways Pay for the War, 

i2mo, 3 00 

Houghton, C. E. The Elements of Mechanics of Materials. i2mo, *2 00 
Houstoun, R. A. Studies in Light Production.i2mo, 200 

























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 21 


Hovenden, F. Practical Mathematics for Young Engineers, 

i2mo, *i 50 

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Howorth, J. Repairing and Riveting Glass, China and Earthen¬ 
ware.8vo, paper, *0 50 

ioyt, W. F. Chemistry by Experimentation. i2mo, *0 70 

Elubbard, E. The Utilization of Wood-waste.8vo, *2 00 

Hubner, J. Bleaching and Dyeing of Vegetable and Fibrous 

Materials. (Outlines of Industrial Chemistry.) .8vo, *5 00 

ludson, O. F. Iron and Steel. (Outlines of Industrial 

Chemistry.) . 8vo, *2 00 

lumphrey, J. C. W. Metallography of Strain. (Metallurgy 

Series) . (In Press.) 


lumphreys, A. C. The Business f eatures of Engineering 


Practice .8vo, *1 25 

lunter, A. Bridge Work.8vo (In Press.) 

lurst, G. H. Handbook of the Theory of Color.8vo, *2 50 

— Dictionary of Chemicals and Raw Products.8vo, *4 50 

— Lubricating Oils, Fats and Greases.8vo, *4 00 

— Soaps.8vo, *5 00 

lurst, G. H., and Simmons, W. H. Textile Soaps and Oils, 

8vo, 3 00 

lurst, H. E., and Lattey, R. T. Text-book of Physics.. . 8vo, *3 00 

— Also published in Three Parts: 

Vol. I. Dynamics and Heat. *1 25 

Vol. II. Sound and Light. *1 25 

Vol. III. Magnetism and Electricity. *1 50 


tutchinson, R. W., Jr. Long Distance Electric Power Trans¬ 
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lutchinson, R. W., Jr., and Thomas, W. A. Electricity in 

Mining. (In Press.) 

lutchinson, W. B. Patents and How to Make Money Out of 

Them . ^mo, 1 00 

lutton, W. S. The Works’ Manager’s Handbook.• 8vo, 6 00 

lyde, E. W. Skew Arches. (Science Series No. 15.).. . i6mo, o 50 

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22 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


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Ingham, A. E. Gearing. A practical treatise.8vo, *2 51 

Ingle, H. Manual of Agricultural Chemistry. 8vo, *3 01 

Inness, C. H. Problems in Machine Design.i2mo, *2 o< 

-Air Compressors and Blowing Engines. i2mo, *2 o< 

--Centrifugal Pumps.i2mo, *2 o< 

-The Fan.i2mo, *2 o< 


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of Storage Reservoirs. (Science Series No. 6.). i6mo, o 5< 
Jannettaz, E. Guide to the Determination of Rocks. Trans. 

by G. W. Plympton..i2mo, 1 5( 

Jehl, F. Manufacture of Carbons..8vo, *4 o< 

Jennings, A. S. Commercial Paints and Painting. (West¬ 
minster Series.) .8vo, *2 o< 

Jennison, F. H. The Manufacture of Lake Pigments.8vo, *3 o< 

Jepson, G. Cams and the Principles of their Construction.. .8vo, *1 5< 

-Mechanical Drawing..8vo {In Preparation. 

Jervis-Smith, F. J. Dynamometers.8vo, *3 5< 

Jockin, W. Arithmetic of the Gold and Silversmith . . . nmo, *1 o< 
Johnson, J. H. Arc Lamps and Accessory Apparatus. (In¬ 
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Johnson, T. M. Ship Wiring and Fitting. (Installation 

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Johnson, W. McA. The Metallurgy of Nickel. {In Preparation 

Johnston, J. F. W., and Cameron, C. Elements of Agricultural 

Chemistry and Geology..i2mo, 2 6c 

Joly, J. Radioactivity and Geology..i2mo, *3 oc 

Jones, H. C. Electrical Nature of Matter and Radioactivity 

i2mo, *2 oc 

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-New Era in Chemistry.i2mo, *2 oc 

Jones, J. H. Tinplate Industry. 8vo, *3 oc 

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Jordan, L. C. Practical Railway Spiral.i2mo, Leather, *1 5c 


























D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 23 


Joynson, F. H. Designing and Construction of Machine Gear¬ 


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juptner,,H. F. V. Siderology: The Science of Iron.8vo, 

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96.). l6mo > 

Kapper, F. Overhead Transmission Lines.4to, 

Keim, A. W. Prevention of Dampness i 1 Bi ildings . =. . 8vo, 


Keller, S. S. Mathematics for Engineering Students. 

i2mo, half leather, 

_and Knox, W. E. Analytical Geometry and Calculus.. 

Kelsey, W. R. Continuous-current Dynamos and Motors. 

8vo, 

Kemble, W. T., and Underhill, C. R. The Periodic Law and the 


Hydrogen Spectrum.8vo, paper, 

Kemp, J. F. Handbook of Rocks. 8vo, 

Kendall, E. Twelve Figure Cipher Code.4to, 

Kennedy, A. B. W., and Thurston, R H. Kinematics of 

Machinery. (Science Series No. 54.).i6mo, 

Kennedy, A. B. W., Unwin, W. C., and Idell, F. E. Compressed 

Air. (Science Series No. 106.).i6mo, 

Kennedy, R. Electrical Installations. Five Volumes. 4 to, 

Single Volumes. each ’ 

_Flying Machines; Practice and Design.izmo, 

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Kennelly, A. E. Electro-dynamic Machinery.8vo, 


Kent, W. Strength of Materials. (Science Series No. 41.). i6mo, 

Kershaw, J. B. C. Fuel, Water and Gas Analysis.. • 8vo, 

_Electrometallurgy. (Westminster Series.).8vo, 

_The Electric Furnace in Iron and Steel Production.. i?mo, 

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oVUj 

Kindelan, J. Trackman’s Helper. I2mo ’ 


2 00 
*5 00 


o 50 

*4 00 
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*2 00 

*2 50 

*0 50 
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42 50 

o 50 

o 50 
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1 50 
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*2 50 
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2 00 






















24 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


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Kirkaldy, A. W., and Evans, A. D. History and Economics 

of Transport.8vo, *3 00 

Kirkaldy, W. G. David Kirkaldy’s System of Mechanical 

Testing.4*o> 10 00 

Kirkbride, J. Engraving for Illustration.8vo, *1 50 

Kirkham, J. E. Structural Engineering.8vo, *5 00 

Kirkwood, J. P. Filtration of River Waters..4to, 7 50 

Kirschke, A. Gas and Oil Engines.i2mo. *1 25 

Klein, J. F. Design of a High speed Steam-engine.8vo, *5 00 

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Klingenberg, G. Large Electric Power Stations.4to, *5 00 

Knight, R.-Adm. A. M. Modern Seamanship...8vo, *650 

Knott, C. G., and Mackay, J. S. Practical Mathematics. . 8vo, 2 00 

Knox, G. D. Spirit of the Soil.i2mo, *1 25 

Knox, J. Physico-chemical Calculations.i2mo. *1 25 

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Koller, T. The Utilization of Waste Products.8vo, *3 00 


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Koppe, S. W. Glycerine.i2mo, *2 50 

Kozmin, P. A. Flour Milling. Trans, by M. Falkner. .8vo, 7 50 

Kremann, R. Application of Phyaico Chemical Theory to 
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Trans, by H. E. Potts.8vo, *3 00 

Kretchmar, K. Yarn and Warp Sizing.8vo, *4 00 

Laffargue, A. The Attack in Trench Warfare.321m), o 50 

Lallier, E. V. Elementary Manual of the Steam Engine. 

i2mo, *2 00 

Lambert, T. Lead and its Compounds.8vo, *3 50 

-Bone Products and Manures.8vo, *3 00 




























£). VAN NOSTRAND company's short-title catalog 25 


Lamborn, L. L. Cottonseed Products.8vo 

-Modern Soaps, Candles, and Glycerin.8vo, 

Lamprecht, R. Recovery Work After Pit Fires. Trans, by 
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Lancaster, M. Electric Cooking, Heating and Cleaning. .8vo, 
Lanchester, F. W. Aerial Flight. Two Volumes. 8vo. 


Vol. I. Aerodynamics . 

Vol. II. Aerodonetics. 

-The Flying Machine.8vo, 

Lange, K. R. By-Products of Coal-Gas Manufacture. .i2mo, 

Larner, E. T. Principles of Alternating Currents.i2mo, 

La Rue, B. F. Swing Bridges. (Science Series No. 107.). i6mo, 
Lassar-Cohn, Dr. Modern Scientific Chemistry. Trans, by M 

M. Pattison Muir.i2mo, 

Latimer, L. H., Field, C. J., and Howell, J, W Incandescent 
Electric Lighting. (Science Series No. 57.)... . .i6mo, 


Latta, M. N. Handbook of American Gas-Engineering Practice. 


8 vo, 

-American Producer Gas Practice.4to, 

Laws, B. C. Stability and Equilibrium of Floating Bodies.Svo, 
Lawson, W. R. British Railways, a Financial and Commer¬ 
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Leask, A. R. Breakdowns at Sea....i2mo, 

-Refrigerating Machinery . .i2mo, 

Lecky, S. T. S. “Wrinkles” in Practical Navigation. .. .8vo, 
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i6mo, 

Leeds, C. C. Mechanical Drawing for Trade Schools.oblong 4to, 

-Mechanical Drawing for High and Vocational Schools, 

4to, 

Lefdvre, L. Architectural Pottery. Trans, by H. K. Bird and 


W. M. Binns. 4to, 

Lehner, S. Ink Manufacture. Trans, by A. Morris and H 
Robson.8vo 


*3 00 
*7 5 o 

*4 00 
*1 00 

. *6 00 
*6 00 
*3 00 
2 00 
*1 25 
o 50 

*2 00 

o 50 

*4 50 
*6 00 
*3 50 

2 00 
2 00 
2 00 
*10 00 

o 50 
*2 00 

*1 25 

*7 50 

*2 50 


Lemstrom, S. Electricity in Agriculture and Horticulture. .8vo, *1 50 
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26 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Le Van, W. B. Steam-Engine Indicator. (Science Series No. 

7 8 .).i 6 mo, o 50 

Lewes, V. B. Liquid and Gaseous Fuels. (Westminster Series.) 


8vo, *2 00 

-Carbonization of Coal. 8v0 > *3 00 

Lewis Automatic Machine Rifle ; Operation of. l6m0 » *o 6o 

Lewis, L. P. Railway Signal Engineering.8vo, *3 5° 

Licks, H. E. Recreations in Mathematics.iamo, 1 25 

Lieber, B. F. Lieber’s Five Letter Standard Telegraphic Code, 

8vo, *10 00 

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---French Edition . 8v0 > * l ° 00 

-terminal Index . 8v0 > * 2 5 ° 

-Lieber’s Appendix ....folio, *15 00 

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Shippers’ Blank Tables . 8v0 > * x 5 00 


Lieber, B. F. 100,000,000 Combination Code.8vo, *10 00 

-Engineering Code.8vo, *12 50 

Livermore, V. P., and Williams, J. HOw to Become a Com¬ 
petent Motorman.i2mo, *1 00 

Livingstone, R. Design and Construction of Commutators.8vo, *2 25 

-Mechanical Design and Construction of Generators. ..8vo, *3 50 

Lloyd, S. L. Fertilizer Materials. (In Press.) 

Lobben, P. Machinists’ and Draftsmen’s Handbook.8vo, 2 50 

Lockwood, T. D. Electricity, Magnetism, and Electro-teleg¬ 
raphy.8vo, 2 50 

-Electrical Measurement and the Galvanometer....i2mo, o 75 

Lodge, 0 . J. Elementary Mechanics..i2mo, 1 50 

-Signalling Across Space without Wires.8vo, *2 00 

Loewenstein, L. C., and Crissey, C. P. Centrifugal Pumps.. *4 50 

Lomax, J. W. Cotton Spinning.i2mo, 1 50 

Lord, R. T. Decorative and Fancy Fabrics. 8 vo, *3 50 

Loring, A. E. A Handbook of the Electromagnetic Telegraph, 

i6mo, o 50 

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Lovell, D. H. Practical Switchwork. Revised by Strong and 

Whitney . (In Press.) 

































D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 27 


Low, D. A. Applied Mechanics (Elementary).i6mo, o 80 

Lubschez, B. J. Perspective.i2mo, *i 50 

Lucke, C. E. Gas Engine Design.. 8 vo, *3 \oo 

-Power Plants: their Design, Efficiency, and Power Costs. 

2 vols. (In Preparation.) 

Luckiesh, M. Color and Its Application.8vo, *3 00 

-Light and Shade and Their Applications.8vo, *2 50 

The two when purchased together. *5 00 

Lunge, G. Coal-tar Ammonia. Three Parts.8vo, *20 00 

-Manufacture of Sulphuric Acid and Alkali. Four Volumes. 

8vo, 

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Vol. I. Supplement. 5 00 

Vol. II. Salt Cake, Hydrochloric Acid and Leblanc Soda. 

In two parts.. - (In Press.) 

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Vol. IV. Electrolytic Methods. '(In Press.) 

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-Technical Methods of Chemical Analysis. Trans, by 

C. A. Keane. In collaboration with the corps of 
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Vol. I. In two parts.8vo, *15 00 

Vol. II. In two parts.8vo, *18 00 

Vol. III. In two parts.8vo, *18 00 

The set (3 vols.) complete. *50 00 

-.Technical Gas Analysis. 8v0 > *4 00 

Luquer, L. M. Minerals in Rock Sections.8vo, *150 

Macewen, H. A. Food Inspection.8vo, *250 

Mackenzie, N. F. Notes on Irrigation Works.8vo, *250 

Mackie, J. How to Make a Woolen Mill Pay.8vo, *200 

Maguire, Wm. R. Domestic Sanitary Drainage and Plumbing 

8vo, 4 00 

Malcolm, C. W. Textbook on Graphic Statics.8vo, *3 00 

Malcolm, H. W. Submarine Telegraph Cable. (In Press.) 

Mallet, A. Compound Engines. Trans, by R. R. Buel. 

(Science Series No. 10.).ibmo, 

































28 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Mansfield, A. N. Electro-magnets. (Science Series No. 64) 

i6mo, 0 5c 

Marks, E. C. R. Construction of Cranes and Lifting Machinery 

i2mo, *1 50 

-Construction and Working of Pumps. nmo, *1 50 

-Manufacture of Iron and Steel Tubes.nmo, *2 00 

-Mechanical Engineering Materials.nmo, *1 00 

Marks, G. C. Hydraulic Power Engineering.8vo, 3 50 

-Inventions, Patents and Designs....nmo, *1 00 

Marlow, T. G. Drying Machinery and Practice.8vo, *500 

Marsh, C. F. Concise Treatise on Reinforced Concrete.. . . 8vo, *2 50 
Marsh, C. F. Reinforced Concrete Compression Member 

Diagram Mounted on Cloth Boards. *1 50 

Marsh, C. F., and Dunn, W. Manual of Reinforced Concrete 
and Concrete Block Construction. ...i6mo, fabrikoid, 

(In Press.) 

Marshall, W.J., and Sankey, H. R. Gas Engines. (Westminster 

Series.).8vo, *2 00 

Martin, G. Triumphs and Wonders of Modern Chemistry. 


8vo, *2 00 

-Modern Chemistry and Its Wonders.8vo, *2 00 

Martin, N. Properties and Design of Reinforced Concrete, 

i2mo, *2 50 

Martin, W. D. Hints to Engineers.i2mo, 1 50 

Massie, W. W., and Underhill, C. R. Wireless Telegraphy and 

Telephony.i2mo ; "i 00 

Mathot, R. E. Internal Combustion Engines.8vo, *4 00 

Maurice, W. Electric Blasting Apparatus and Explosives ..8vo, *3 50 

-Shot Firer’s Guide..g v0 *1 50 

Maxwell, F. Sulphitation in White Sugar Manufacture. i2mo, 3 00 
Maxwell, J. C. Matter and Motion. (Science Series No. 36.) 

i6mo, 0 50 

Maxwell, W. H., and Brown, J. T. Encyclopedia of Municipal 

and Sanitary Engineering... 4 to, *10 co 

Mayer, A. M. Lecture Notes on Physics.8vo, 2 00 

Mayer, C., and Slippy, J. C. Telephone Line Construction. 8vo, *3 00 

McCullough, E. Practical Surveying.i2mo, *200 

-Engineering Work in Cities and Towns.8vo, *300 

-—-Reinforced Concrete . I2mo * x 50 






















D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 2g 


McCullough, R. S. Mechanical Theory of Heat. .8vo, 

McGibbon, W. C. Indicator Diagrams for Marine Engineers, 

-Marine Engineers’ Drawing Book.oblong 4 to,’ 

-Marine Engineers’ Pocketbook.i2mo, leather, 

McIntosh, J. G. Technology of Sugar.. .svo*, 

-Industrial Alcohol.8 V0 

-Manufacture of Varnishes and Kindred Industries. * 

Three Volumes. 8vo. 


3 50 

*3 50 
*2 50 
*4 00 
*5 00 
*3 00 


Vol. I. Oil Crushing, Refining and Boiling .. 

Vol. II. Varnish Materials and Oil Varnish Making. 

Vol. III. Spirit Varnishes and Materials. 

McKay, C. W. Fundamental Principles of the Telephone 

Business .8vo, (In Press.) 

McKillop, M., and McKillop, D. A. Efficiency Methods. 

i2mo, 1 50 

McKnight, J. D., and Brown, A. W. Marine Multitubular 


Boilers. * r g 0 

McMaster, J. B. Bridge and Tunnel Centres. (Science Series 

No. 20.).i6mo, o 53 


McMechen, F. L. Tests for Ores, Minerals and Metals.. .i2mo, *r 00 

McPherson, J. A. Water-works Distribution.8vo, 2 50 

Meade, A. Modern Gas Works Practice.8vo, *7 50 

Meade, R. K. Design and Equipment of Small Chemical 

Laboratories .. *.8vo, 

Melick, C. W. Dairy Laboratory Guide.i2mo *1 25 

Mensch, L. J. Reinforced Concrete Pocket Book. i6mo, leather *400 
Merck, E. Chemical Reagents: Their Purity and Tests. 

Trans, by H. E. Schenck.8vo, 1 00 

Merivale, J. H. Notes and Formulae for Mining Students, 

i2mo, 1 50 

Merritt, Wm. H. Field Testing for Gold and Silver. i6mo, leather, 1 50 
Mertens, Colonel. Tactics and Technique in River Crossings. 


Translated by Major Walter Krueger.8vo, 2 50 

Mierzinski, S. Waterproofing of Fabrics. Trans, by A. Morris 

and H. Robson.8vo, *2 50 

Miessner, B. F. Radiodynamics.i2mo, *2 00 

Miller, G. A. Determinants. (Science Series No. 105.). . i6mo, 

Miller, W. J. Historical Geology.,..i2mo, *200 

Mills, C. N. Elementary Mechanics for Engineers.i2mo, *1 00 

Milroy, M. E, W. Home Lace-making....nmo, *1 00 


*3 50 
*4 GO 
*4 5o 



























30 D. VAN NOSTRAND COMPANY S SHORT-TITLE CATALOG 

Mitchell, C. A. Mineral and Aerated Waters.8vo, *3 oc 

-and Prideaux, R. M. Fibres Used in Textile and 

Allied Industries.8vo, *3 00 

Mitchell, C. F. and G. A. Building Construction and Draw¬ 
ing... i2mo 

Elementary Course, *1 50 

Advanced Course, *2 50 

Monckton, C. C. F. Radiotelegraphy. (Westminster Series.) 

8vo, *2 00 

Monteverde, R. D. Vest Pocket Glossary of English-Spanish, 

Spanish-English Technical Terms.64010, leather, *1 00 

Montgomery, J. H. Electric Wiring Specifications.... i6mo, *1 00 
Moore, E. C. S. New Tables for the Complete Solution of 

Ganguillet and Kutter’s Formula.8vo, *5 00 

Morecroft, J. H., and Hehre, F. W. Short Course in Electrical 

Testing .8vo, *1 50 

Morgan, A. P. Wireless Telegraph Apparatus for Amateurs, 

i2mo, *1 50 

Moses, A. J. The Characters of Crystals ..8vo, *2 00 

-and Parsons, C. L. Elements of Mineralogy.8vo, *3 00 

Moss, S. A. Elements of Gas Engine Design. (Science 

Series No. 121).i6mo, o 50 

-The Lay-out of Corliss Valve Gears. (Science Series 

No. 119.) .i6rao, o 50 

Mulford, A. C. Boundaries and Landmarks.i2mo, *1 00 

Mullin, J. P. Modern Moulding and Pattern-making. . . i2mo, 2 50 

Munby, A. E. Chemistry and Physics of Building Materials. 

(Westminster Series.).8vo, *2 00 

Murphy, J. G. Practical Mining..i6mo, 1 00 

Murray, J. A. Soils and Manures. (Westminster Series.).8vo, *2 00 


Nasmith, J. The Student’s Cotton Spinning.8vo, 3 00 

-Recent Cotton Mill Construction.i2mo, 2 50 

Neave, G. B., and Heilbron, I. M. Identification of Organic 

Compounds.i2mo, *1 25 

Neilson, R. M. Aeroplane Patents.8vo, *2 00 





















D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 31 


Nerz, F. Searchlights. Trans, by C. Rodgers.8vo, 

Heuberger, H., and Noalhat, H. Technology of Petroleum. 

Trans, by J. G. McIntosh...8vo, 

Newall, J. W. Drawing, Sizing and Cutting Bevel-gears. .8vo, 
Newbiging, T. Handbook for Gas Engineers and Managers, 

8vo, 

Newell, F. H., and Drayer, C. E. Engineering as a Career. 

121110, cloth, 
paper, 

Nicol, Q. Ship Construction and Calculations.8vo, 

Nipher, F. E. Theory of Magnetic Measurements.i2mo, 

Nisbet, H. Grammar of Textile Design..8vo, 

Nolan, H. The Telescope. (Science Series No. 51.).i6mo, 

Norie, J. W. Epitome of Navigation.octavo, 

—*—A Complete Set of Nautical Tables with Explanations 

of Their Use.octavo, 

North, H. B. Laboratory Experiments in General Chemistry 

i2ino, 

Nugent, E. Treatise on Optics..nmo, 

O’Connor, H. The Gas Engineer’s Pocketbook. . nmo, leather, 
Ohm, G. S., and Lockwood, T. D. Galvanic Circuit. Trans, by 
William Francis. (Science Series No. 102.). . . . i6mo, 
Olsen, J. C. Textbook of Quantitative Chemical Analysis. .8vo, 
Olsson, A. Motor Control, in Turret Turning and Gun Elevating. 

(U. S. Navy Electrical Series, No. 1.). ...i2mo, paper, 

Ormsby, M. T. M. Surveying.121310, 

Oudin, M. A. Standard Polyphase Apparatus and Systems .. 8vo, 
Owen, D. Recent Physical Research.8vo, 

Pakes, W. C. C., and Nankivell, A. T. The Science of Hygiene. 

8 vo, 

Palaz, A. Industrial Photometry. Trans, by G. W. Patterson, 

Jr.Bvo, 

Pamely, C. Colliery Manager’s Handbook..8vo, 

Parker, P. A. M. The Control of Water.8vo, 

Parr, G. D. A. Electrical Engineering Measuring Instruments. 

8vo, 

Parry, E. J. Chemistry of Essential Oils and Artificial Per¬ 
fumes.. 


*3 00 

*10 00 
1 50 

*6 50 

*1 00 
o 75 
*5 00 
1 00 
*3 00 
o 50 
8 00 

6 50 

*1 00 
1 50 

3 50 

0 50 
*3 50 

*0 50 
1 50 
*3 00 
*1 50 


*1 75 

*4 00 
*10 00 
• *5 00 

*3 5o 

Press.) 



















32 D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 


Parry, E J. Foods and Drugs. Two Volumes.8vo, 

Vol. I. Chemical and Microscopical Analysis of Food 

and Drugs. *7.50 

Vol. II. Sale of Food and Drugs Acts. *3 00 

-and Coste, J. H. Chemistry of Pigments.8vo, *4 50 

Parry, L. Notes on Alloys.8vo, *3 00 

-Metalliferous Wastes .8vo, *2 00 

-Analysis of Ashes and Alloys.8vo, *2 00 

Parry, L. A. Risk and Dangers of Various Occupations.8vo, *3 00 

Parshall, H. F., and Hobart, H. M. Armature Windings .. 4to, ' *7 50 

-Electric Railway Engineering.4to, *10 00 

Parsons, J. L. Land Drainage.8vo, *1 50 

Parsons, S. J. Malleable Cast Iron.8vo, *2 50 

Partington, J. R. Higher Mathematics for Chemical Students 

i2mo, *2 00 

-Textbook of Thermodynamics.8vo, *4 00 

Passmore, A. C. Technical Terms Used in Architecture .. .8vo, *3 50 

Patchell, W. H. Electric Power in Mines.8vo, *4 00 

Paterson, G. W. L. Wiring Calculations.i2mo, *2 00 

-Electric Mine Signalling Installations.i2mo, *1 50 

Patterson, D. The Color Printing of Carpet Yarns.8vo, *3 50 

Color Matching on Textiles.8vo, *3 00 

-Textile Color Mixing.8vo, *3 00 

Paulding, C. P. Condensation of Steam in Covered and Bare 

Pipes-.8vo, *2 00 

-Transmission of Heat Through Cold-storage Insulation 

i2mo, *1 00 

Payne, D. W. Founders’ Manual..8vo, *4 00 

Peckham, S. F. Solid Bitumens.8vo, *5 00 

Peddie, R. A. Engineering and Metallurgical Books_nmo, *1 50 

Peirce, B. System of Analytic Mechanics. . 4 to, 1000 

-Linnear Associative Algebra. 4 to, 3 00 

Pendred, V. The Railway Locomotive. (Westminster Series.) 

8vo, *2 00 

Perkin, F. M. Practical Method of Inorganic Chemistry.. i2mo, *1 00 

— and Jaggers, E. M. Elementary Chemistry.i2mo, *1 00 

Perrin, J. Atoms.8vo, *2 50 

Perrine, F. A. C. Conductors for Electrical Distribution . .. 8vo, *3 50 





























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 33 


Petit, G. White Lead and Zinc White Paints. 8vo, 

Petit, R. How to Build an Aeroplane. Trans, by T. O’B. 

Hubbard, and J. H. Ledeboer.8vo, 

Pettit, Lieut. J. S. Graphic Processes. (Science Series No. 76.) 

i6mo, 

Philbrick, P. H. Beams and Girders. (Science Series No. 88.) 


i6mo, 

Phillips, J. Gold Assaying.8vo, 

-Dangerous Goods. 8vo, 

Phin, J. Seven Follies of Science....i2mo, 

Pickworth, C. N. The Indicator Handbook. Two Volumes 

i2mo, each, 

-Logarithms for Beginners.i2mo, boards, 

-The Slide Rule. I2mo > 

Plattner’s Manual of Blowpipe Analysis. Eighth Edition, re¬ 
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Plympton, G.W. The Aneroid Barometer. (Science Series.).i6mo, 

_How to become an Engineer.* (Science Series No. 100.) 

i6mo, 


__Van Nostrand’s Table Book. (Science Series No. 104). 

i6mo, 

Pochet, M. L. Steam Injectors. Translated from the French. 

(Science Series No. 29.).i6mo, 

Pocket Logarithms to Four Places. (Science Series.)-i6mo, 

bather, 

Polleyn, F. Dressings and Finishings for Textile Fabrics.8vo, 

Pope, F. G. Organic Chemistry. I2m0 > 

Pope,* F. L. Modern Practice of the Electric Telegraph-8vo, 

Popplewell, W. C. Prevention of Smoke.8vo, 

_Strength of Materials. 8v0 > 

Porritt, B. D. The Chemistry of Rubber. (Chemical Mono¬ 
graphs, No. 3.). I2mo ’ 

Porter, J. R. Helicopter Flying Machine. I2mo > 

Potts, H. E. Chemistry of the Rubber Industry. (Outlines of 

Industrial Chemistry.). 8v0 > 

Practical Compounding of Oils, Tallow and Grease 8vo, 


*1 50 
*1 50 
o 50 


*2 50 
3 50 
*1 25 

1 50 
o 50 
1 00 

*4 00 
o 50 

o 50 

O 50 

o 50 
o 50 

I 00 

*3 00 
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*1 00 
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*2 50 
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34 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 


Pratt, K. Boiler Draught.i2mo, *i 25 

-High Speed Steam Engines.8vo, *2 00 

Pray, T., Jr. Twenty Years with the Indicator.8vo, 2 50 

-Steam Tables and Engine Constant...8vo, 2 00 

Prelini, C. Earth and Rock Excavation.8vo, *3 00 

-Graphical Determination of Earth Slopes.8vo, *2 00 

-Tunneling. .. . 8vo, *3 00 

-Dredging. A Practical Treatise.8vo, *3 00 

Prescott, A. B. Organic Analysis...8vo, 5 00 

-and Johnson, 0 . C. Qualitative Chemical Analysis.8vo, *3 50 

-and Sullivan, E. C. First Book in Qualitative Chemistry 

i2mo, *1 50 

Prideaux, E. B. R. Problems in Physical Chemistry.8vo, *200 

-Theory and Us3 of Indicators.8vo, 5 00 

Prince, G. T. Flow of Water.i2mo, *2 00 

Pullen, W. W. F. Application of Graphic Methods to the Design 

of Structures.i2mo, *2 50 

-Injectors: Theory, Construction and Working..nmo, *1 50 

-Indicator Diagrams .8vo, *2 50 

-Engine Testing .8vo, *4 50 

Putsch, A. Gas and Coal-dust Firing.8vo, *3 00 

Pynchon, T. R. Introduction to Chemical Physics.8vo, 3 00 

Rafter, G. W. Mechanics of Ventilation. (Science Series No. 

33 *).i6mo, o 50 

-Potable Water. (Science Series No. 103.).i6mo, o 50 

--Treatment of Septic Sewage. (Science Series No. 118.) 

i6mo, o 50 

-and Baker, M. N. Sewage Disposal in the United States 

4to, *6 00 

Raikes, H. P. Sewage Disposal Works.8vo, *4 00 

Randau, P. Enamels and Enamelling.8vo, *4 00 

Rankine, W. J. M. Applied Mechanics.8vo, 5 00 

-- Civil Engineering. 8vo ’ 6 50 

-Machinery and Millwork.g vo> ^ 00 

-The Steam-engine and Other Prime Movers.8vo, 5 00 

-and Bamber, E. F. A Mechanical Textbook.8vo, 3 50 




































D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 35 


Ransome, W. R. Freshman Mathematics.i2mo, *i 35 

Raphael, F. C. Localization of Faults in Electric Light and 

Power Mains....*.8vo, *3 5° 

Rasch, E. Electric Arc Phenomena. Trans, by K. Tornberg. 

8vo, *2 00 

Rathbone, R. L. B. Simple Jewellery.8vo, *200 

Rateau, A. Flow of Steam through Nozzles and Orifices. 

Trans, by H. B. Brydon..8vo, *1 50 

Rausenberger, F. The Theory of the Recoil of Guns-8vo, *4 5° 

Rautenstrauch, W. Notes on the Elements of Machine Design, 

8vo, boards, *1 50 

Rautenstrauch, W., and Williams, J. T. Machine Drafting and 


Empirical Design. 

Part I. Machine Drafting...8vo, *1 25 

Part II. Empirical Design. (In Preparation.) 

Raymond, E. B. Alternating Current Engineering.izmo, *2 50 

Rayner, H. Silk Throwing and Waste Silk Spinning. ..8vo, *2 50 

Recipes for the Color, Paint, Varnish, Oil, Soap and Drysaltery 

Trades . 8v0 > *3 50 

Recipes for Flint Glass Making.i2mo, *4 5 ° 

Redfern, J. B., and Savin, J. Bells, Telephones. (Installa¬ 
tion Manuals Series.).i6mo, *0 50 

Redgrove, H. S. Experimental Mensuration.i2mo, ¥ i 25 

Redwood, B. Petroleum. (Science Series No. 92.)-i6mo, o 50 

Reed, S. Turbines Applied to Marine Propulsion. *5 00 

Reed’s Engineers’ Handbook. 8v0 » *9 00 

_Key to the Nineteenth Edition of Reed’s Xngineers’ 

Handbook . 8v0 > *4 00 

_Useful Hints to Sea-going Engineers.mmo, 3 00 

Reid, E. E. Introduction to Research in Organic Chemistry. 


Reid H A Concrete and Reinforced Concrete Construction, 

8vo, *5 00 

Reinhardt, C. W. Lettering for Draftsmen, Engineers, and 

Students.^ blon g 4 t0 > boards ’ 1 00 

_ Xhe Technic of Mechanical Drafting, .oblong 4 to, boards, *1 00 



















36 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 
Reiser, F. Hardening and Tempering of Steel. Trans, by A. 


Morris and H. Robson.i2mo, *2 50 

Reiser, N. Faults in the Manufacture of Woolen Goods. Trans. 

by A. Morris and H. Robson .8vo, *2 50 

-Spinning and Weaving Calculations.8vo, *5 00 

Renwick, W. G. Marble and Marble Working.8vo, 5 00 

Reuleaux, F. The Constructor. Trans, by H. H. Suplee. -4to, *4 00 

Reuterdahl, A. Theory and Design of Reinforced Concrete 

Arches ..^ ,.8vo, *200 

Rey, J. Range of Electric Searchlight Projectors.8 vo, *4 5 ° 

Reynolds, 0 ., and Idell, F. E. Triple Expansion Engines. 

(Science Series No. 99.).i6mo, o 50 

Rhead, G. F. Simple Structural Woodwork.i2mo, *1 00 

Rhodes, H. J. Art of Lithography.8 vo, 3 50 

Rice, J. M., and Johnson, W. W. A New Method of Obtaining 

the Differential of Functions.i2mo, o 50 

Richards, W. A. Forging of Iron and Steel.i2mo, 1 50 

Richards, W. A., and North, H. B. Manual of Cement Testing, 

i2mo, *1 50 

Richardson, J. The Modern Steam Engine.8vo, *3 50 

Richardson, S. S. Magnetism and Electricity.i2mo, *2 00 

Rideal, S. Glue and Glue Testing.8vo, *4 00 

Riesenberg, F. The Men on Deck.i2mo, 3 00 

Rimmer, E. J. Boiler Explosions, Collapses and Mishaps.8vo, *1 75 

Rings, F. Concrete in Theory and Practice.i2mo, *2 50 

-Reinforced Concrete Bridges.4to, *5 00 


Ripper, W. Course of Instruction in Machine Drawing... folio, *6 00 
Roberts, F. C. Figure of the Earth. (Science Series No. 79.) 

i6mo, o 50 

Roberts, J., Jr. Laboratory Work in Electrical Engineering 


8vo, *2 00 

Robertson, L. S. Water-tube Boilers.8vo, 2 00 

Robinson, J. B. Architectural Composition.8vo, *2 50 

Robinson, S. W. Practical Treatise on the Teeth of Wheels. 

(Science Series No. 24.).i6mo, o 50 

-Railroad Economics. (Science Series No. 59.)_i6mo, o 50 

Wrought Iron Bridge Members. (Science Series No. 

60.)....i6mo, o 50 
























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 37 

Robson, J. H. Machine Drawing and Sketching.8vo, 2 00 

Roebling, J. A. Long and Short Span Railway Bridges. . folio, 25 00 
Rogers, A. A Laboratory Guide of Industrial Chemistry. 8vo, 2 00 

-Elements of Industrial Chemistry.i2mo, 3 00 

-Manual of Industrial Chemistry.8vo, *5 00 

Rogers, F. Magnetism of Iron Vessels. (Science Series No. 30.) 

j6mo, o 50 

Rohland, P. Colloidal and its Crystalloidal State of Matter. 

Trans, by W. J. Britland and H. E. Potts i2mo, *1 25 

Rollinson, C. Alphabets.otrteag i2mo, *1 00 

Rose, J. The Pattern-makers’ Assistant.8vo, 2 50 

-Key to Engines and Engine-running.i2mo, 2 50 

Rose, T. K. The Precious Metals. (Westminster Series.).. 8vo, *2 00 
Rosenhain, W. Glass Manufacture. (Westminster Series.).. 8vo, *2 00 
——Physical Metallurgy, An Introduction to. (Metallurgy 


Series.) .8vo, *3 50 

Roth, W. A. Physical Chemistry.8vo, *2 00 

Rowan, F.J. Practical Physics of the Modern Steam-boiler.8vo, *3 00 

-and Idell, F. E. Boiler Incrustation and Corrosion. 

(Science Series No. 27.)....i6mo, o 50 

Roxburgh, W. General Foundry Practice. (Westminster 

Series.) .8vo, *2 00 

Ruhmer, E. Wireless Telephony. Trans, by J. Erskine- 

Murray.. 8 vo, *3 50 

Russell, A. Theory of Electric Cables and Networks.8vo, *3 00 

Rutley, F. Elements of Mineralogy.iamo, *1 25 

Sanford, P. G. Nitro-explosives.8vo, *4 00 

Saunders, C. H. Handbook of Practical Mechanics. i6mo, 1 00 

leather, 1 25 

Sayers, H. M. Brakes for Tram Cars.8vo, *1 25 

Scheele, C. W. Chemical Essays.8vo, *-2 00 

Scheithauer, W. Shale Oils and Tars.8vo, *3 50 

Scherer, R. Casein. Trans, by C. Salter.8vo, *300 

























38. D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 

Schidrowitz, P. Rubber, Its Production and Industrial Uses, 

8vo, *5 00 

Schindler, K. Iron and Steel Construction Works.i2mo, *1 25 

Schmall, C. N. First Course in Analytic Geometry, Plane and 

Solid.i2mo, half leather, *1 75 

Schmeer, L. Flow of Water.8vo, *3 00 

Schumann, F. A Manual of Heating and Ventilation. 

i2mo, leather, 1 50 

Schwartz, E. H. L. Causal Geology.8vo, *2 50 

Schweizer, V. Distillation of Resins.8vo, *4 50 

Scott, W. W. Qualitative Analysis. A Laboratory Manual, 

New Edition.(/« Press.) 

-Standard Methods of Chemical Analysis.8vo, *6 00 

Scribner, J. M. Engineers’ and Mechanics’ Companion. 

i6mo, leather, 1 50 

Scudder, H. Electrical Conductivity and Ionization Constants 

of Organic Compounds.8vo, *3 00 

Searle, A. B. Modem Brickmaking.8vo, *5 00 

-Cement, Concrete and Bricks.8vo, *3 00 

Searle, G. M. “ Sumners’ Method.” Condensed and Improved. 

(Science Series No. 124.).i6mo, o 50 

Seaton, A. E. Manual of Marine Engineering.8vo, 8 00 

Seaton, A. E., and Rounthwaite, H. M. Pocket-book of Marine 

Engineering .i6mo, leather, 3 50 

Seeligmann, T., Torrilhon, G. L., and Falconnet, H. India 
Rubber and Gutta Percha. Trans, by J. G. McIntosh 


8vo, *5 00 

Seidell, A. Solubilities of Inorganic and Organic Substances, 

8vo, *3 00 

Seligman, R. Aluminum. (Metallurgy Series). (In Press.) 

Sellew, W. H. Steel Rails. 4 to, *10 00 

-Railway Maintenance Engineering.i2mo, *2 50 

Senter, G. Outlines of Physical Chemistry.12010, *2 00 

-Textbook of Inorganic Chemistry.i2mo, *1 75 

Sever, G. F. Electric Engineering Experiments .. . 8vo, boards, *100 
— and Townsend, F. Laboratory and Factory Tests in Elec¬ 
trical Engineering.. f .. 8vo, *2 50 
























D. VAN NOSTRAND COMPANY^ SHORT-TITLE CATALOG 39 


Sewall, C. H. Wireless Telegraphy. 


*2 

00 

-Lessons in Telegraphy. 

i2mo, 

*1 

00 

Sewell, T. The Construction of Dynamos. 


*3 

00 

Sexton, A. H. Fuel and Refractory Materials. 

i2mo, 

*2 

50 

Chemistry of the Materials of Engineering. . 

12 mo, 

*2 

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-Alloys (Non-Ferrous).. 

. . 8vo, 

*3 

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-and Primrose, J. S. G. The Metallurgy of Iron and 

Steel, 



8vo, 

*6 

50 

Seymour, A. Modern Printing Inks. 

.. 8vo, 

*2 

00 

Shaw, Henry S. H. Mechanical Integrators. (Science 

Series 



No. 83.) .. 

. i6mo, 

0 

50 

Shaw, S. History of the Staffordshire Potteries. 

,. .8vo, 

2 

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Chemistry of Compounds Used in Porcelain Manufacture.8vo, 

*5 

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Shaw, T. R. Driving of Machine Tools. 

. i2mo, 

*2 

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. i2mo, 

4 

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Shaw, W. N. Forecasting Weather. 

.. 8vo, 

*3 

5° 

Sheldon, S., and Hausmann, E. Direct Current Machines 

.12010, 

*2 

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-Alternating-current Machines . 

. i2mo, 

*2 

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--Electric Traction and Transmission Engineering. 

. i2mo, 

*2 

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-Physical Laboratory Experiments. 


*1 

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Shields, J. E. Note on Engineering Construction. 

i2mo, 

1 

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Shreve, S. H. Strength of Bridges and Roofs ... 8vo, 3 50 

Shunk, W. F. The Field Engineer.i2mo, fabrikoid, 2 50 

Simmons, W. H., and Appleton, H. A. Handbook of Soap 

Manufacture. 8vo, *3 00 

Simmons, W. H., and Mitchell, C. A. Edible Fats and Oils, 

8 vo, *3 00 

Simpson, G. The Naval Constructor.izmo, fabrikoid, *5 00 

Simpson, W. Foundations.Bvo (In Press.) 

Sinclair, A. Development of the Locomotive Engine. 

8vo, half leather, 5 00 

Sindall, R. W. Manufacture of Paper. (Westminster Series.) 

8vo, *2 00 

_and Bacon, W. N. The Testing of Wood.Pulp... .8vo, *2 50 

Sloane, T. O’C. Elementary Electrical Calculations.i2mo, *2 00 

Smallwood, J. C. Mechanical Laboratory Methods. (Van 

Nostrand’s Textbooks.).iamo, fabrikoid, *3 00 

Smith C. A. M. Handbook of Testing, MATERIALS 8vo, *2 50 

_and Warren, A. G. New Steam Tables.8vo, *1 25 

Smith, C. F. Practical Alternating Currents and Testing.8vo, *3 50 
_ Practical Testing of Dynamos and Motors.8vo, *3 00 































40 D. VAN NOSTRAND COMPANY'S SHORT-TITLE CATALOG 




Smith, F. A. Railway Curves.121110, *i oo 

-Standard Turnouts on American Railroads.i2mo, *i oo 

-Maintenance of Way Standards.i2mo, *i 50 


Smith, F. E. Handbook of General Instruction for Mechanics. 


i2mo, 1 50 

Smith, H. G. Minerals and the Microscope.i2mo, *1 25 

Smith, J. C. Manufacture of Paint.8vo, *3 50 

Smith, R. H. Principles of Machine Work.i2tno, 

-Advanced Machine Work.i2mo, *3 00 

Smith, W. Chemistry of Hat Manufacturing.i2mo, *300 

Snell, A. T. Electric Motive Power. 8 vo, *4 00 

Snow, W. G. Pocketbook of Steam Heating and Ventilation, 

(In Press.) 

Snow, W. G., and Nolan, T. Ventilation of Buildings. (Science 

Series No. 5.).i6mo, 050 

Soddy, F. Radioactivity.8vo, *3 00 

Solomon, M. Electric Lamps. (Westminster Series.)-8vo, *200 

Somerscales, A. N. Mechanics for Marine Engineers. .i2mo, *2 00 

-Mechanical and Marine Engineering Science.8vo, *5 00 

Sothern, J. W. The Marine Steam Turbine.8vo, *6 00 

-Verbal Notes and Sketches for Marine Engineers-8vo, *9 00 

Sothern, J. W., and Sothern, R. M. Elementary Mathematics 

for Marine Engineers......i2mo, *1 50 

-Simple Problems in Marine Engineering Design. .i2mo, *1 50 

Southcombe, J. E. Chemistry of the Oil Industries. (Out¬ 
lines of Industrial Chemistry).8vo, *3 00 

Soxhlet, D. H. Dyeing and Staining Marble. Trans, by A. 

Morris and H. Robson..8vo, *2 50 

Spangenburg, L. Fatigue of Metals. Translated by S. H. 

Shreve. (Science Series No. 23.).i6mo, o 50 

Specht, G. J., Hardyj A. S., McMaster, J. B., and Walling. Topo¬ 
graphical Surveying. (Science Series No. 72.). i6mo, # o 50 

Spencer, A. S. Design of Steel-Framed Sheds.8vo, *3 50 

Speyers, C. L. Text-book of Physical Chemistry.8vo, *1 50 


Spiegel, B. Chemical Constitution and Physiological Action. 

(Trans, by C. Luede>ing and A. C. Boylston.) . i2mo, *1 25 
































D VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 4 1 


Sprague, E. H. Elementary Mathematics for Engineersiamo, i 50 

--Elements of Graphic Statics. 8 vo, 2 00 

Sprague, E. H. Hydraulics. I2m0 > 1 5 ° 

-Stability of Arches. I2m0 > 1 5 ° 

-Stability of Masonry.121110, 1 5 ° 

f, _Strength of Structural Elements...izrno, 1 75 

Stahl, A W. Transmission of Power. (Science Series No. 28.) 

i6mo, 

._ an d Woods, A. T. Elementary Mechanism.i2mo, *2 00 

Staley, C., and Pierson, G. S. The Separate System of 

Sewerage . 8v0 » 

Standage, H. C. Leatherworkers’ Manual.8vo, 

,_Sealing Waxes, Wafers, and Other Adhesives.8vo, 

_Agglutinants of All Kinds for All Purposes.i2mo, 

Stanley, H. Practical Applied Physics. (In Press.) 

Stansbie, J. H. Iron and Steel. (Westminster Series.) . .8vo, *2 00 

Steadman, F. M. Unit Photography. I2m0 > " 2 00 

Stecher, G. E. Cork. Its Origin and Industrial Uses..i2mo, 1 00 
Steinman, D. B. Suspension Bridges and Cantilevers. 

(Science Series No. 127.)..... 

_Melan’s Steel Arches and Suspension Bridges 

Stevens, E. J. Field Telephones and Telegraphs for Army 


*3 00 
*3 50 
*2 00 
*3 50 


o 50 
.8vo, *3 00 


Use 


Stevens, H. P. Paper Mill Chemist. l6 ™°’ 

Stevens, J. S. Theory of Measurements. I2tno ’ 

Stevenson, J. L. Blast-Furnace Calculations. ,nmo, leather, 

Stewart, G. Modern Steam Traps. I2mo > 

Stiles, A. Tables for Field Engineers. I2mo ’ 

Stodola, A. Steam Turbines. Trans by L. C. Loewenstein.Svo, 

Stone, H. The Timbers of Commerce... 8v0 ’ 

Slopes, M. Ancient Plants. 


1 20 
*2 50 
*1 25 
*2 00 
*1 25 
1 00 
*5 00 
3 50 
*2 00 


The Study of Plant Life! 1 T.!... ^ * 2 00 


Sudborough J J., and James, T. C. Practical Organic Chem- 


Suffling E H. Treatise on the Art of Glass Painting. .. .8vo, 
SuUivan, T. V., and Underwood, N. Testing and Valuation 

of Building and Engineering Materials . C gl *7 io 

Sur F T. S. Oil Prospecting and Extracting. > 

Svenson, C. L. Handbook of Piping.. — J ^ 

and Trade' Marks.' '(Westminster ^ ^ 
Series.) . 


*2 00 
*3 50 





































42 D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 


Swinburne, J., Wordingham, C. H., and Martin, T. C. Electric 


Currents. (Science Series No. 109.).i6mo, o 50 

Swoope, C. W. Lessons in Practical Electricity.12010, *2 00 


*6 00 


o 50 


*2 50 
*2 50 
*2 00 
*1 00 

*0 


3 00 


*2 50 


Tailfer, L. Bleaching Linen and Cotton Yarn and Fabrics.Svo, 

Tate, J. S. Surcharged and Different Forms of Retaining- 

walls. (Science Series No. 7.).iGxno, 

Taylor, F, N. Small Water Supplies.i2mo, 

--Masonry in Civil Engineering.8vo, 

Taylor, T. U. Surveyors Handbook.i2mo, leather, 

-Backbone of Perspective.i2mo, 

Taylor, W. P. Practical Cement Testing.8vo, 

Templeton, W. Practical Mechanic’s Workshop Companion, 

i2ino, morocco, 

Tenney, E. H. Test Methods for Steam Power Plants. 

(Van Nostrand’s Textbooks.).i2mo, 

Terry, H. L. India Rubber and its Manufacture. (West¬ 
minster Series.). 8vo, 

Thayer, H. R. Structural Design.8vo, 

Vol. I. Elements of Structural Design. 00 

Vol. II. Design of Simple Structures. *4 00 

Vol. III. Design of Advanced Structures. (In Preparation.) 

-Foundations and Masonry. (In Preparation.) 

Thiess, J. B., and Joy, G. A. Toll Telephone Practice. .8vo, *3 50 
Thom, C., and Jones, W. H. Telegraphic Connections, 

oblong i2mo, 1 50 

Thomas, C. W. Paper-makers’ Handbook. ..(In Press.) 

Thomas, J. B. Strength of Ships.8vo, 3 ^ 

Thompson, A. B. Oil Fields of Russia.4to, 


*2 00 


-Oil Field Development and Petroleum Mining.. . 8vo, 

Thompson, S. P. Dynamo Electric Machines. (Science 

Series No. 75.).i6mo, 

Thompson, W. P. Handbook of Patent Law of All Countries, 


*7 50 


*7 50 


o 50 


i6mo, 1 50 

Thomson, G. Modern Sanitary Engineering.i2mo, *3 00 

Thomson, G. S. Milk and Cream Testing.i2mo, *1 75 


Modern Sanitary Engineering, House Drainage, etc. .8vo, *3 00 
























D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 43 


Thornley, T. Cotton Combing Machines.8vo, *3 00 

-Cotton Waste . 8v0 > *3 00 

-Cotton Spinning . 8 vo, 

First Year . * J 5o 

Second Year . *3 00 

Third Year . ’ t ' 2 5 ° 

Thurso, J. W. Modern Turbine Practice.8vo, *4 00 

Tidy, C. Meymott. Treatment of Sewage. (Science Series 

No. 94.) . l6rao > 0 5 o 

Tillmans, J. Water Purification and Sewage Disposal. Trans. 

by Hugh S. Taylor. 3 vo, *2 00 

Tinney, W. H. Gold-mining Machinery.8vo, *3 00 

Titherley, A. W. Laboratory Course of Organic Chemistry.8vo, *2 00 

Tizard, H. T. Indicators. On Press.) 

Toch, M. Chemistry and Technology of Paints.8vo, *4 00 

-Materials for Permanent Painting.i2mo, *2 00 

Tod, J., and McGibbon, W. C. Marine Engineers’ Board of 

Trade Examinations .8vo, '2 00 

Todd, J., and Whall, W. B. Practical Seamanship.8vo, 8 00 

Tonge, J. Coal. (Westminster Series.).8vo, *200 

Townsend, F. Alternating Current Engineering. . 3 vo, boards, *0 75 

Townsend, J. Ionization of Gases by Collision.8vo, *1 25 

Transactions of the American Institute of Chemical Engineers. 

Eight volumes now ready. Vols. I. to IX., 1908-1916, 

8vo, each, *6 00 

Vol. X. (In Press.) 

Traverse Tables. (Science Series No. 115.). l6m0 > 0 5 ° 

mor., 1 00 

Treiber, E. Foundry Machinery. Trans, by C. Salter.. i2ino, *1 50 
Trinks, W., and Housum, C. Shaft Governors. (Science 

Series No. 122.). l6m0 ' 0 5 ° 

Trowbridge, D. C. Handbook for Engineering Draughtsmen.^^ ^ 

Trowbridee W. P. Turbine Wheels. (Science Series No. 44 .) 

6 9 i6mo, o 50 

Tucker, J. H. A Manual of Sugar Analysis.8vo, 3 5? 

Tunner, P. A. Treatise on Roll-turning. Trans, by J. 3 . 

’ . . 8v0 text and folio atlas ’ 10 00 



























( 


44 D. VAN NOSTRAND COMPANY’S SHORT-TITLE CATALOG 

Turnbull, Jr., J., and Robinson, S. W. A Treatise on the 
Compound Steam-engine. (Science Series No. 8 .) 

i 6 mo, 

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Turrill, S. M. Elementary Course in Perspective.12010, *1 25 

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